CONTEXT.—: Bullous dermatophytosis is a rare blistering disorder resulting from fungal infection. Limited literature describes the clinical and microscopic features of this disease. OBJECTIVE.—: To summarize the histopathologic and clinical features of 25 biopsy-proven cases of bullous tinea. DESIGN.—: The study was a single-center retrospective review of patients diagnosed with bullous dermatophyte infection by skin biopsy. RESULTS.—: Bullous tinea is rarely suspected clinically in biopsy-proven cases, often mimicking other spongiotic disorders that can vesiculate. In addition to classically taught histopathologic clues, several unique characteristics were observed in our population. The presence of dermal neutrophils as the nonpredominant cell type (85%; n = 17 of 20) can serve as an additional clue to diagnosis. Deep inflammation (25%; n = 5 of 20) does not exclude a superficial diagnosis. The classically taught sandwich sign (32%; n = 8 of 25) may be less relevant in the setting of bullous tinea. Hyphae were most commonly seen within the stratum corneum adjacent to this blister rather than within the blister itself, and special staining was required in a substantial number of cases (40%; n = 10 of 25) to reach the correct diagnosis. CONCLUSIONS.—: Bullous tinea is unusual but should be considered in the differential diagnosis of blistering skin disorders. Hematoxylin and eosin-stained slides frequently lack obvious fungal hyphae; for this reason, periodic acid-Schiff reaction or Gomori/Grocott methenamine silver stains should be routinely considered for biopsies showing intraepidermal and/or subepidermal blister formation and prominent neutrophil infiltration to prevent misdiagnosis.

CONTEXT.—: Pathology training is focused on the attainment of clinical, diagnostic, and administrative skills. Preparation for employment search and the interview process are often neglected. Given that a near majority of pathology trainees in the United States are graduates of foreign medical schools, training in the job search and interview process according to local customs, norms, and expectations has greater salience for individuals new to the United States. OBJECTIVE.—: To offer perspectives on 2 components of the job search process: (1) finding a suitable job opening in academic and private practice settings and (2) preparing for an interview. We have provided a set of common interview questions and suggested preparatory methodology. The differences in the process and expectations in academic settings and private practice operations are highlighted. Engaging in the job search process early and networking are emphasized. We have also suggested approaches for pathology teachers and mentors in guiding trainees in a job search and preparation for an interview. DATA SOURCES.—: The information and opinions expressed in this communication are based on the personal experiences of 4 senior pathologists in academic and private practice settings. CONCLUSIONS.—: Start networking early. Leverage contacts with teachers, attendings, senior residents, and people at national meetings to locate appropriate job opportunities. Seek assistance from attendings in preparing a curriculum vitae and cover letter. Prepare for the questions that may come up in an interview. A dress rehearsal for an interview is strongly recommended.

CONTEXT.—: Nonsalivary primary adenocarcinomas of the base of tongue (PABOTs) are extremely rare and worth reporting. OBJECTIVE.—: To study the detailed clinicopathologic features of PABOT. DESIGN.—: Cases of PABOT diagnosed on pathology material were retrieved from the archived electronic surgical pathology records. RESULTS.—: Six cases in 4 men and 2 women (M:F ratio, 2:1), with an age range of 31 to 76 years, satisfied the criteria. The tumor epicenter was the base of tongue in all (6 of 6; 100%), with extension to the epiglottis in 50% (3 of 6), nodal metastasis in 66.7% (4 of 6), and distant metastasis in 33.3% (2 of 6). On histology, all but one were pure adenocarcinoma. Five of 6 cases (83.3%) had a gastrointestinal (GI) phenotype, of which 2 (40%) had a colonic/lower-GI-type (small groups of cells floating in mucin, CK20+, SATB2+, and CDX2+) and 3 (60%) had an upper-GI-like adenocarcinoma (UGI-LA; malignant glands with intracellular mucin, CK7+) histology. Cystic structure suggestive of teratomatous origin was identified in 2 of 5 cases (40%), both with UGI-LA phenotype. The non-GI-type case had a unique histology with squamous differentiation in addition to adenocarcinoma areas, diffuse nuclear β-catenin on immunohistochemistry, and a corresponding exon 3 CTNNB1 mutation. One patient succumbed to disease, and 4 are alive with disease (follow-up of 1-9 months after completion of therapy). CONCLUSIONS.—: We suggest using the broad term primary adenocarcinomas of the base of tongue (PABOTs), which can be further subdivided into colonic-type adenocarcinoma of the tongue and oral cavity, UGI-LA, and not otherwise specified categories, and reiterate a need for recognition and distinction of PABOT from salivary gland tumors. A subset originates from teratoid/duplication cysts, necessitating extensive sampling. Multicentric studies are essential to clinically and biologically prognosticate each of these categories.

CONTEXT.—: Mitochondria and mitochondrial DNA have been suggested to play a role in cancer initiation and progression. Knowledge of mitochondrial DNA could provide a breakthrough to advance cancer management. OBJECTIVE.—: To identify the mitochondrial DNA landscape in non-small cell lung carcinoma. DESIGN.—: The adenocarcinoma set consisted of 365 pairs of adenocarcinomas and normal lung tissues, whereas the metastasis set included 12 primary non-small cell carcinomas, 15 metastatic tumors, and their normal counterparts. Tumor-specific somatic variants were identified, and if a variant showed heteroplasmy, the proportion of minor alleles was evaluated. Variants with greater than 10% change in allele frequency between tumor and normal pairs were identified as "heteroplasmic shifts." RESULTS.—: Tumor-specific variants appeared throughout the whole mitochondrial genome, without a common hot spot. Distinct variant profiles were seen in 289 (79.18%) of all individual adenocarcinomas. The presence of a unique profile and the number and loading of heteroplasmic shifts in tumors increased with higher stage or lymph node metastasis, and were related to shorter survival. In the metastasis set, the primary tumor variants were generally found in metastatic tumors. CONCLUSIONS.—: This study shows that somatic mitochondrial DNA mutations present with diverse locations and unique profiles in each individual tumor, implying their clinicopathologic utility.

CONTEXT.—: Extramedullary hematopoiesis (EMH) is an uncommon occurrence, usually associated with hematologic disorders, but it rarely presents as an isolated finding. OBJECTIVE.—: To determine the frequency, immunomorphologic features, and clinicopathologic background of EMH in orchiectomies from pediatric patients. DESIGN.—: All orchiectomy specimens removed from children from 2008 to 2020 in our institution were retrospectively reviewed. Biopsies and neoplasias were excluded. The EMH diagnosis was rendered when hematopoietic cell precursors were present. Immunohistochemical stainings were performed to characterize the hematopoietic components. RESULTS.—: Seventy-nine orchiectomies from 77 children (mean age, 5 years; range, 0-17 years) were included in our study. Forty-three patients (55.8%) underwent surgery for testicular atrophy, 30 (39.0%) for torsion, and 4 (5.2%) for intersex conditions. EMH was identified in 6 of 79 orchiectomies (7.6%), all performed for testicular torsion. All patients but one were newborns, and the remaining patient was 15 years old. No patient had evidence of a hematologic disorder. All EMH foci were in a background of reactive changes with a variable extension, either in the epididymis (4 cases) or in the deferens duct (2 cases). Immunostaining confirmed an association of myeloid (myeloperoxidase+) and erythroid precursors (E-cadherin+) in all 6 cases. One case also presented rare megakaryocytes, and one showed benign TdT+ B-cell precursors. CONCLUSIONS.—: To our knowledge, this is the first study that demonstrates EMH as a common finding in orchiectomy samples, especially from newborns. Despite the lack of pathologic potential, it is important to recognize EMH in order to avoid misdiagnosis.

CONTEXT.—: The World Health Organization Classification of Tumours: Female Genital Tract Tumors, 5th edition, published in September 2020, comes 6 years after the 4th edition, and reflects the monumental leaps made in knowledge about the biology of gynecological tumors. Major changes include revised criteria for the assignment of the site of origin of ovarian and fallopian tube tumors, a revision in the classification of squamous and glandular lesions of the lower genital tract based on human papillomavirus association, and an entire chapter devoted to genetic tumor syndromes. This article highlights the changes in the 5th edition relative to the 4th edition, with a focus on areas of value to routine clinical practice. OBJECTIVE.—: To provide a comprehensive update on the World Health Organization classification of gynecological tumors, highlighting in particular updated diagnostic criteria and terminology. DATA SOURCES.—: The 4th and 5th editions of the World Health Organization Classification of Tumours. CONCLUSIONS.—: The World Health Organization has made several changes in the 5th edition of the update on female genital tumors. Awareness of the changes is needed for pathologists' translation into contemporary practice.

CONTEXT.—: Anatomic pathologists render diagnosis on tissue samples sectioned onto glass slides and viewed under a bright-field microscope. This approach is destructive to the sample, which can limit its use for ancillary assays that can inform patient management. Furthermore, the subjective interpretation of a relatively small number of 2D tissue sections per sample contributes to low interobserver agreement among pathologists for the assessment (diagnosis and grading) of various lesions. OBJECTIVE.—: To evaluate 3D pathology data sets of thick formalin-fixed Barrett esophagus specimens imaged nondestructively with open-top light-sheet (OTLS) microscopy. DESIGN.—: Formalin-fixed, paraffin-embedded Barrett esophagus samples (N = 15) were deparaffinized, stained with a fluorescent analog of hematoxylin-eosin, optically cleared, and imaged nondestructively with OTLS microscopy. The OTLS microscopy images were subsequently compared with archived hematoxylin-eosin histology sections from each sample. RESULTS.—: Barrett esophagus samples, both small endoscopic forceps biopsies and endoscopic mucosal resections, exhibited similar resolvable structures between OTLS microscopy and conventional light microscopy with up to a ×20 objective (×200 overall magnification). The 3D histologic images generated by OTLS microscopy can enable improved discrimination of cribriform and well-formed gland morphologies. In addition, a much larger amount of tissue is visualized with OTLS microscopy, which enables improved assessment of clinical specimens exhibiting high spatial heterogeneity. CONCLUSIONS.—: In esophageal specimens, OTLS microscopy can generate images comparable in quality to conventional light microscopy, with the advantages of providing 3D information for enhanced evaluation of glandular morphologies and enabling much more of the tissue specimen to be visualized nondestructively.

CONTEXT.—: Low-risk (Gleason score 3 + 3 = 6) and intermediate-risk (Gleason score 3 + 4 = 7) prostate carcinoma cases diagnosed on needle biopsies are frequently referred for gene expression studies such as Oncotype DX to help validate the risk. Risk assessment helps determining prognosis and therapeutic decision making. OBJECTIVE.—: To determine if addition of molecular testing is necessary, by evaluating its correlation with risk stratification provided by pathology report (Gleason score, grade group, proportion of positive cores) and serum prostate-specific antigen (PSA) level. DESIGN.—: Our institutional database was searched for cases that had Oncotype DX testing after prostate biopsy. The final risk category determined by molecular testing was compared to the risk stratification predicted by the pathology report and serum PSA levels. Cases were classified as concordant if they fell under the same National Comprehensive Cancer Network risk and recommended initial therapy group. Follow-up information on discordant cases was obtained and used to determine if risk stratification by molecular testing was superior to that obtained from the clinicopathologic data. RESULTS.—: A total of 4967 prostate biopsies (2015-2020) were screened. Of these, 131 prostate carcinoma cases (2.6%) had Oncotype DX testing and 111 of 131 cases (85%) had follow-up information. There was risk stratification concordance in 93 of 111 cases (84%). All 18 of 111 cases (16%) that were discordant had a follow-up course that matched the risk predicted by pathology data and serum PSA. CONCLUSIONS.—: Risk stratification provided by information in the pathology report on routine biopsy assessment coupled with the serum PSA level is equivalent to that obtained by Oncotype DX testing.

CONTEXT.—: Pancreatic ductal adenocarcinoma has some of the worst prognostic outcomes among various cancer types. Detection of histologic patterns of pancreatic tumors is essential to predict prognosis and decide the treatment for patients. This histologic classification can have a large degree of variability even among expert pathologists. OBJECTIVE.—: To detect aggressive adenocarcinoma and less aggressive pancreatic tumors from nonneoplasm cases using a graph convolutional network-based deep learning model. DESIGN.—: Our model uses a convolutional neural network to extract detailed information from every small region in a whole slide image. Then, we use a graph architecture to aggregate the extracted features from these regions and their positional information to capture the whole slide-level structure and make the final prediction. RESULTS.—: We evaluated our model on an independent test set and achieved an F1 score of 0.85 for detecting neoplastic cells and ductal adenocarcinoma, significantly outperforming other baseline methods. CONCLUSIONS.—: If validated in prospective studies, this approach has a great potential to assist pathologists in identifying adenocarcinoma and other types of pancreatic tumors in clinical settings.

CONTEXT.—: Endometrial cancer is classified into 4 molecular subtypes: DNA polymerase epsilon ultramutated, mismatch repair deficient, p53 mutant, and nonspecific molecular profile (NSMP). Additional biomarkers are urgently needed to better characterize the NSMP subtype, the largest group with heterogeneous pathologic features and prognoses. OBJECTIVE.—: To investigate the expression of B7 homolog 3 (B7-H3), B7 homolog 4 (B7-H4), and V-set and immunoglobulin domain containing 3 (VSIG-3, a ligand for B7-H5) in 833 patients with endometrial cancer and determine their associations with clinicopathologic and molecular features as well as survival outcomes. DESIGN.—: Molecular classification was determined by polymerase epsilon sequencing and immunohistochemical staining for p53 and mismatch repair proteins. B7-H3, B7-H4, VSIG-3, and programmed death ligand-1 (PD-L1) were detected via immunohistochemistry. RESULTS.—: The positivity rates for B7-H3 in each of tumor and immune cells, B7-H4 (exclusively in tumor cells), and VSIG-3 (exclusively in tumor cells) were 89.0%, 42.3%, 71.5%, and 99.8%, respectively. B7-H3 and B7-H4 positivity in tumor cells was associated with favorable pathologic features and prognosis. In contrast, B7-H3 expression in immune cells was frequent in samples with unfavorable pathologic features; those with p53-mutant subtype, PD-L1 positivity, and a high density of CD8+ T cells; and in patients with poor prognoses. Positive B7-H4 expression was a predictor of improved survival in patients with the NSMP subtype independent of tumor stage or pathologic features. CONCLUSIONS.—: The NSMP subgroup of endometrial cancer can be further stratified by B7-H4 status. Incorporating B7-H4 status into the molecular classification of NSMP could improve the ability to predict disease relapse.

CONTEXT.—: Because of restrictions as a result of the COVID-19 pandemic, medical educators rapidly transitioned to an online curriculum for pathology resident education. The benefits and challenges of the shift to online learning, as well as strategies to maximize learning, are yet to be fully elucidated. OBJECTIVE.—: To assess learner perception and satisfaction with the move to online learning. Understanding the benefits of online learning will allow future curricular changes to most effectively incorporate online learning. Understanding the common challenges will allow our current learning strategies to rapidly adapt and ideally mitigate these challenges as online learning is incorporated into medical education. DESIGN.—: This was a survey-based study distributed by email to residents nationwide in Canada in anatomic pathology, general pathology, neuropathology, and hematopathology. Thirty residents participated, from anatomic pathology (n = 23; 76%), from general pathology (n = 5; 16%), and 1 participant each from hematopathology and neuropathology. RESULTS.—: All participants indicated that their program had transitioned to online learning at least in part. The majority of participants (n = 16; 53%) did not feel their pathology education was negatively affected by the transition to online learning; however, a significant minority (n = 6; 20%) felt their education had been negatively affected. Convenience and less intimidation were rated as benefits of online learning. Negative effects included technical issues and decreased engagement; we identified a number of strategies used by programs and residents to mitigate these negative effects. CONCLUSIONS.—: Our survey points to a need to use adaptations and best-practice recommendations to maximize the benefits of online learning moving forward.

CONTEXT.—: Progressive independence in medicine is critical to building confidence and decisiveness in trainees. However, this can be difficult to accomplish in the strict regulatory environment of pathology. OBJECTIVE.—: To pilot and adopt a process whereby surgical pathology fellows independently manage a subset of cases and release preliminary reports. DESIGN.—: Upon program approval, board-certified surgical pathology fellows were eligible for preliminary report sign-out at their discretion. Eligible cases were sent from outside institutions for confirmatory review. Preliminary reports were viewable in the electronic medical record. Safety measures were used to ensure timely release of final reports by attending pathologists. RESULTS.—: Fellows participating in the pilot (n = 4) released 59 preliminary reports out of 101 cases reviewed (58%), with 1 potentially significant discrepancy between preliminary and final report. Turnaround time was not affected. The process was endorsed by all participants and adopted as standard practice. During the first year, eligible fellows (n = 8) released 123 preliminary reports out of 1260 cases reviewed (9.8%). There were no major diagnostic discrepancies and no effects on turnaround time. The number of preliminary reports released by each fellow was variable (range, 2-48; median, 8), likely a reflection of both external factors (number of trainees on service, volume) and trainee-specific factors (confidence, efficiency). CONCLUSIONS.—: Fellows showed good judgment when independently managing cases, with just 1 potentially significant discrepancy out of 182 cases (<1%). No patients were adversely impacted. Use of this process varied widely among fellows and may require closer monitoring and encouragement for fellows who are tentative about releasing preliminary reports.

CONTEXT.—: Discrete submucosal necrotic nodules may rarely manifest as colon polyps. OBJECTIVE.—: To characterize the clinical and pathologic features of this lesion, which has been under-studied in the literature. DESIGN.—: We conducted an international search to compile a series. For each potential case, photomicrographs were centrally reviewed to confirm the diagnosis. We gathered clinical and pathologic information on each confirmed case. RESULTS.—: The final cohort included 25 patients, with 23 having 1 lesion and 2 having several (31 lesions total). Mean patient age was 62 years; 13 (52%) were male. Symptoms were nonspecific, although 4 patients (16%) had blood in stool; 14 patients were asymptomatic. Patient history and medications appeared noncontributory. Most cases were located in the right colon (n = 18; 58%). Mean size was 0.4 cm (range, 0.1-1.7 cm). Histology typically showed a centrally necrotic nodule with peripheral fibrosis, chronic inflammation, and sometimes palisading granulomatous inflammation. Percent necrosis ranged from 5% to 95% (average, 70%), and percent fibrosis ranged from 3% to 70% (average, 25%). In 3 cases, degenerated parasitic structures consistent with Anisakis could be seen on hematoxylin-eosin and trichrome special stain. No patient experienced disease recurrence. CONCLUSIONS.—: Submucosal necrotic nodules can present as colon polyps. Most cases are unifocal, and patients do well on follow-up. At least some examples appear to be caused by Anisakis, implicating patient diet. Patients are often asymptomatic, and many cases show no histologic evidence of the causative agent.

CONTEXT.—: Recently, new technologies, such as next-generation sequencing and third-generation sequencing, have been used in carrier screening of thalassemia. However, there is no direct comparison between the 2 methods in carrier screening of thalassemia. OBJECTIVE.—: To compare the clinical performance of third-generation sequencing with next-generation sequencing in carrier screening of thalassemia. DESIGN.—: Next-generation sequencing and third-generation sequencing were simultaneously conducted for 1122 individuals in Hainan Province. RESULTS.—: Among 1122 genetic results, 1105 (98.48%) were concordant and 17 (1.52%) were discordant between the 2 methods. Among the 17 discordant results, 4 were common thalassemia variants, 9 were rare thalassemia variants, and 4 were variations with unknown pathogenicity. Sanger sequencing and polymerase chain reaction for discordant samples confirmed all the results of third-generation sequencing. Among the 685 individuals with common and rare thalassemia variants detected by third-generation sequencing, 512 (74.74%) were carriers of α-thalassemia, 110 (16.06%) were carriers of β-thalassemia, and 63 (9.20%) had coinheritance of α-thalassemia and β-thalassemia. Three thalassemia variants were reported for the first time in Hainan Province, including -THAI, -α2.4, and ααααanti3.7. Eleven variants with potential pathogenicity were identified in 36 patients with positive hemoglobin test results. Among 52 individuals with negative hemoglobin test results, 17 were identified with thalassemia variants. In total, third-generation sequencing and next-generation sequencing correctly detected 763 and 746 individuals with variants, respectively. Third-generation sequencing yielded a 2.28% (17 of 746) increment compared with next-generation sequencing. CONCLUSIONS.—: Third-generation sequencing was demonstrated to be a more accurate and reliable approach in carrier screening of thalassemia compared with next-generation sequencing.

CONTEXT.—: Distinguishing true antemortem thrombus (AMT) from artifactual postmortem clot (PMC) can occasionally be challenging at autopsy. Lines of Zahn are cited as pathognomonic of AMT, but review of literature reveals heterogeneous definitions of the term. Neutrophil karyorrhexis and CD61 immunohistochemistry can also be used to define AMT, but there has been no systematic study determining the specificity of these features. OBJECTIVE.—: To identify features that distinguish AMT from PMC, and to clarify the definition of lines of Zahn. DESIGN.—: PMC from the heart was collected in 50 hospital autopsies. Fifty arterial and 50 venous surgical thrombectomy specimens were reviewed for comparison. The microscopic features with hematoxylin-eosin staining, phosphotungstic acid-hematoxylin (PTAH) staining, and CD61 immunohistochemistry were documented. RESULTS.—: Thin curvilinear strands of fibrin and clumps of fibrin were frequently observed in both AMT and PMC. Thick bands of nested platelets wrapped in fibrin were nearly exclusive to AMT. Neutrophil karyorrhexis was readily apparent on low power in AMT but was seen in 40 of 50 PMCs (80%) only sparsely on high-power examination. Bone marrow elements were identified in 38 of 50 PMCs (76%). CD61 staining showed a geographic pattern in AMT and a speckled pattern in PMC. PTAH staining confirmed features seen with hematoxylin-eosin. CONCLUSIONS.—: Thin curvilinear strands of fibrin are found in both AMT and PMC and can be misinterpreted as lines of Zahn. We define lines of Zahn as thick bands formed by nested platelets wrapped in fibrin. Diffuse neutrophil karyorrhexis is common in AMT; in contrast, bone marrow elements are often seen in PMC.

CONTEXT.—: Mucinous lesions of the breast encompass many entities ranging from benign to malignant and nonneoplastic to neoplastic. Lesions discussed under this category are mucocele-like lesion, mucinous carcinoma, mucinous micropapillary carcinoma, solid papillary carcinoma, mucinous cystadenocarcinoma, mucoepidermoid carcinoma, invasive lobular carcinoma with extracellular mucin, mucinous ductal carcinoma in situ, and metastasis. OBJECTIVE.—: To review clinical, pathologic, and molecular features of mucinous lesions of the breast, their differential diagnoses, and challenging features on core needle biopsies. DATA SOURCES.—: The existing scientific and clinical literature as of December 2021. CONCLUSIONS.—: The category of mucinous lesions of the breast is vast and the differential diagnosis can be challenging, especially on core needle biopsies. In all cases, clinical, radiologic, and pathologic correlation is necessary to reach a comprehensive diagnosis. Given that the prognosis and management of each entity is different, being aware of these entities and their nuances is critical for a pathologist to guide accurate management.

CONTEXT.—: This review article derives from the breast pathology lecture at the Eighth Princeton Integrated Pathology Symposium (PIPS VIII). OBJECTIVE.—: To provide a literature review and update on fibroepithelial lesions of the breast with molecular findings and findings regarding the pediatric population. DATA SOURCES.—: The sources include extensive literature review, personal research, and experience. CONCLUSIONS.—: Given significant differences in prognosis and management of fibroepithelial lesions, we aim to provide readers with pertinent definitions, pathomorphology, molecular findings, and management for each diagnosis, with insights on the pediatric population.

CONTEXT.—: Appropriate patient management requires precise and meaningful tumor classification. Breast cancer classification continues to evolve from traditional morphologic evaluation to more sophisticated systems with the integration of new knowledge from research being translated into practice. Breast cancer is heterogeneous at the molecular level, with diversified patterns of gene expression, which is presumably responsible for the difference in tumor behavior and prognosis. Since the beginning of this century, new molecular technology has been gradually applied to breast cancer research on issues pertinent to prognosis (prognostic signature) and therapeutic prediction (predictive signature), and much progress has been made. OBJECTIVE.—: To summarize the current state and the prospective future of molecular classification of breast cancer. DATA SOURCES.—: Sources include recent medical literature on molecular classification of breast cancer. CONCLUSIONS.—: Identification of intrinsic tumor subtypes has set a foundation for refining the breast cancer molecular classification. Studies have explored the genetic features within the intrinsic cancer subtypes and have identified novel molecular targets that led to the innovation of clinical assays to predict a patient's prognosis and to provide specific guidelines for therapeutic decisions. With the development and implication of these molecular tools, we have remarkably advanced our knowledge and enhanced our power to provide optimal management to patients. However, challenges still exist. Besides accurate prediction of prognosis, we are still in urgent need of more molecular predictors for tumor response to therapeutic regimes. Further exploration along this path will be critical for improving a patient's prognosis.

CONTEXT.—: Spindle cell lesions of the breast represent a broad spectrum of entities, ranging from nonneoplastic reactive conditions to high-grade malignant tumors. The wide range makes breast spindle cell lesions a diagnostic pitfall. OBJECTIVE.—: To review the classification of spindle cell lesions of the breast, including clinical features, morphologic characteristics, and the role of immunohistochemistry as well as molecular tools in assisting the differential diagnosis. A diagnostic algorithm will be proposed. DATA SOURCES.—: Literature and personal experience are the sources for this study. CONCLUSIONS.—: Spindle cell lesions of the breast can be classified as biphasic or monophasic, with the former including both spindle cell and epithelial components, and the latter including only spindle cell elements. Each category is further subclassified as low or high grade. In the biphasic low-grade group, fibroadenoma and benign phyllodes tumor are the most common lesions. Other uncommon lesions include hamartoma, adenomyoepithelioma, and pseudoangiomatous stromal hyperplasia. In the biphasic high-grade group, borderline/malignant phyllodes tumor and biphasic metaplastic carcinoma are the main lesions to consider. In the monophasic low-grade group, reactive spindle cell nodule, nodular fasciitis, myofibroblastoma, fibromatosis, and fibromatosis-like metaplastic carcinoma have to be considered. In the monophasic high-grade group, the possible lesions are monophasic spindle cell metaplastic carcinoma, primary breast sarcoma, and metastases. Awareness of the clinical history and careful evaluation of any epithelial differentiation (with a large immunohistochemical panel) are crucial in the distinction.

CONTEXT.—: Intraductal carcinoma of the prostate (IDC-P) is considered a distinct form of aggressive prostate cancer where comedonecrosis, a grade 5 pattern, is occasionally present. Meanwhile, assigning a Gleason grade to IDC-P remains controversial. OBJECTIVE.—: To assess the clinical significance of necrosis associated with IDC-P. DESIGN.—: We compared radical prostatectomy (RP) findings and oncologic outcomes in men with prostate cancer exhibiting IDC-P with (IDC-P+/N+) versus without (IDC-P+/N-) comedonecrosis. RESULTS.—: Of the 558 RPs examined, IDC-P was present in 213 cases (38.2%), including 167 (78.4%) with IDC-P+/N- and 46 (21.6%) with IDC-P+/N+. When comparing IDC-P+/N- versus IDC-P+/N+ cases, the presence of necrosis was significantly associated with higher tumor grade, higher incidence of pT3/pT3b or pN1 disease, and larger estimated tumor volume. Outcome analysis revealed a significantly higher risk of disease progression in IDC-P+/N+ patients than in IDC-P+/N- patients (P < .001). Significant differences in progression-free survival between IDC-P+/N- and IDC-P+/N+ patients were also seen in subgroups, such as those without (P = .01) or with (P = .03) adjuvant therapy immediately after RP, those with pN0 disease (P < .001), and, more interestingly, those exhibiting conventional Gleason pattern 5 component (P = .02). Multivariate analysis showed significance for IDC-P+/N+ when IDC-P (grade 4) and IDC-P+/N+ (grade 5) were (hazard ratio, 1.768; P = .049) or were not (hazard ratio, 2.000; P = .008) incorporated into the Gleason score. CONCLUSIONS.—: IDC-P+/N+ was found to be associated with worse histopathologic features on RP and poorer prognosis as an independent predictor. Pathologists may thus need to report the presence or absence of not only IDC-P but also comedonecrosis within IDC-P.

CONTEXT.—: Although CD30 testing is an established tool in the diagnostic workup of lymphomas, it is also emerging as a predictive biomarker that informs treatment. The current definition of CD30 positivity by immunohistochemistry is descriptive and based on reactivity in lymphomas that are defined by their universal strong expression of CD30, rather than any established threshold. Challenges include inconsistencies with preanalytic variables, tissue processing, pathologist readout, and with the pathologist and oncologist interpretation of reported results. OBJECTIVE.—: To develop and propose general best practice recommendations for reporting CD30 expression by immunohistochemistry in lymphoma biopsies to harmonize practices across institutions and facilitate assessment of its significance in clinical decision-making. DESIGN.—: Following literature review and group discussion, the panel of 14 academic hematopathologists and 2 clinical/academic hematologists/oncologists divided into 3 working groups. Each working group was tasked with assessing CD30 testing by immunohistochemistry, CD30 expression readout, or CD30 expression interpretation. RESULTS.—: Panel recommendations were reviewed and discussed. An online survey was conducted to confirm the consensus recommendations. CONCLUSIONS.—: CD30 immunohistochemistry is required for all patients in whom classic Hodgkin lymphoma and any lymphoma within the spectrum of peripheral T-cell lymphoma are differential diagnostic considerations. The panel reinforced and summarized that immunohistochemistry is the preferred methodology and any degree of CD30 expression should be reported. For diagnostic purposes, the interpretation of CD30 expression should follow published guidelines. To inform therapeutic decisions, report estimated percent positive expression in tumor cells (or total cells where applicable) and record descriptively if nontumor cells are positive.

CONTEXT.—: Programmed death ligand-1 (PD-L1) immunohistochemistry companion diagnostic assays play a crucial role as predictive markers in patients being considered for immune checkpoint inhibitor therapy. However, because of a convergence of several factors, including recognition of increased types of cancers susceptible to immunotherapy, increasing numbers of immune checkpoint inhibitors, and release of multiple PD-L1 immunohistochemistry antibodies with differing reporting systems, this complex testing environment has led to significant levels of confusion for pathologists and medical oncologists. OBJECTIVE.—: To identify which processes and procedures have contributed to the current challenges surrounding programmed death receptor-1 (PD-1)/PD-L1 companion diagnostics and to propose potential remedies to this issue. This is based upon input from key industrial stakeholders in conjunction with the College of American Pathologists Personalized Health Care Committee. DESIGN.—: A meeting of representatives of pharmaceutical and in vitro diagnostic companies along with the Personalized Health Care Committee reviewed the process of release of the PD-L1 companion diagnostic assays using a modified root cause analysis format. The modified root cause analysis envisioned an ideal circumstance of development and implementation of a companion diagnostic to identify shortcomings in the rollout of the PD-L1 assay and to suggest actions to improve future companion diagnostic assay releases. RESULTS.—: The group recommended improvements to key principles in companion diagnostics implementation related to multi-stakeholder communication, increased regulatory flexibility to incorporate postapproval medical knowledge, improved cross-disciplinary information exchange between medical oncology and pathology societies, and enhanced postmarket training programs. CONCLUSIONS.—: The rapidly changing nature of and increasing complexity associated with companion diagnostics require a fundamental review of processes related to their design, implementation, and oversight.

CONTEXT.—: Timely reperfusion improves the recovery of patients with acute ischemic stroke. Laboratory results are crucial to guide treatment decisions in patients when abnormal laboratory tests are suspected. OBJECTIVE.—: To implement a new laboratory workflow for acute stroke patients and compare laboratory turnaround time (TAT) preimplementation and postimplementation. DESIGN.—: We conducted a retrospective pre-post intervention study of patients with suspected acute stroke during the 4-month periods before and after the implementation of a new laboratory workflow process. The improvement process included relocating the specimen registration site, laboratory notification before specimen arrival, a color-coding system on tubes, timing at all processes, and eliminating the smear review if platelets were normal. TATs of the laboratory and door-to-clinical intervention times before and after the improvement process were compared. RESULTS.—: Postintervention, median specimen transportation time decreased from 11 (interquartile range [IQR], 8.4-16.4) to 9 minutes (IQR, 6.3-12.8), P < .001. The intralaboratory and total TATs of complete blood cell count, coagulation tests, and creatinine significantly decreased (P < .001 for all). Blood drawn-to-laboratory reported time decreased from 43 (IQR, 36.0-51.5) to 33 minutes (IQR, 29.2-35.8, P < .001). However, door-to-needle time for thrombolysis and door-to-puncture time and door-to-recanalization time for mechanical thrombectomy were not statistically different (P = .11, .69, and .50, respectively). CONCLUSIONS.—: The new laboratory workflow significantly decreased transportation time, TAT of individual tests, and the blood drawn-to-laboratory reported time. However, the time to treatment of acute ischemic stroke patients was not different between preimplementation and postimplementation.

CONTEXT.—: Underuse of laboratory testing has been previously investigated in preselected populations, such as documented malpractice claims. However, these numbers might not reflect real-life situations. OBJECTIVE.—: To evaluate the underuse and misuse of laboratory follow-up testing in a real-life hospital patient population with microcytic anemia, using laboratory results ordered during routine patient care. DESIGN.—: From all patients in whom a microcytic anemia was detected during routine diagnostics in 2018, all available laboratory data were collected and screened for appropriateness of diagnostic workup of iron deficiency and thalassemia. Subgroup analysis was performed for patient groups with mean corpuscular volume values 75 to 79 μm3 (group 1), 65 to 74 μm3 (group 2), and <65 μm3 (group 3). RESULTS.—: A total of 2244 patients with microcytic anemia were identified. Follow-up testing for iron deficiency was not performed in 761 cases (34%). For inconclusive ferritin levels due to elevated C-reactive protein results (n = 336), reticulocyte hemoglobin content or soluble transferrin receptor levels were missing in 86 cases (26%). In patients with suspected thalassemia (n = 127), follow-up testing for hemoglobin variants was not performed in 70 cases (55%). Subgroup analysis showed that the frequency of underuse of iron status as well as thalassemia/hemoglobinopathy testing decreased from group 1 to group 3. When considering relevant preexisting anemia diagnoses, laboratory tests were underused in 904 cases (40.3%). CONCLUSIONS.—: Because 40% (n = 904) of the patients with microcytic anemia were potentially not followed up correctly, laboratory specialists are advised to act by implementing demand management strategies in collaboration with clinicians to overcome underuse of laboratory tests and to improve patient safety.

Comment in Arch Pathol Lab Med. 2023 Jan 1;147(1):15-16.

CONTEXT.—: Pancreatic neuroendocrine tumors (PanNETs) are heterogeneous tumors with a wide range of malignant potential. Therefore, identification of prognostic factors is essential. OBJECTIVE.—: To systematically assess the significance of tumor border, a well-known prognostic indicator in other cancers, in PanNETs. DESIGN.—: We evaluated the macroscopic growth pattern (expansile [Exp] versus infiltrative [Inf]) and the microscopic tumor border (pushing [Pus] versus Inf) of 203 surgically resected PanNETs and compared them with other clinicopathologic factors. RESULTS.—: Based on macroscopic growth pattern, 83 cases had Exp patterns whereas 84 had Inf patterns. According to microscopic tumor border, 122 PanNETs had Pus borders whereas 81 had Inf borders. Combining macroscopic growth pattern and microscopic tumor border, 65 PanNETs had Exp/Pus, 34 had Inf/Pus, 18 had Exp/Inf, and 50 had Inf/Inf status. PanNETs with Inf/Inf status were associated with higher tumor grade, pT classification, and American Joint Committee on Cancer stage grouping; lymph node metastasis; and lymphovascular and perineural invasions (all P < .001). Patients with PanNET having Inf/Inf status had significantly shorter overall survival (OS) and recurrence-free survival (RFS; all P < .001). Further, using multivariate analysis, Inf/Inf status was identified as an independent poor prognostic factor of OS (P = .02) and RFS (P = .03). CONCLUSIONS.—: In summary, combined Inf/Inf status was observed in approximately 25% of PanNETs and was associated with aggressive biological behavior and short OS and RFS. Therefore, assessing combined macroscopic growth pattern and microscopic tumor border can provide additional information regarding survival and recurrence in PanNET patients.

CONTEXT.—: Modern RHD genotyping can be used to determine when patients with serologic weak D phenotypes have RHD gene variants at risk for anti-D alloimmunization. However, serologic testing, RhD interpretations, and laboratory management of these patients are quite variable. OBJECTIVE.—: To obtain interlaboratory comparisons of serologic testing, RhD interpretations, Rh immune globulin (RhIG) management, fetomaternal hemorrhage testing, and RHD genotyping for weak D-reactive specimens. DESIGN.—: We devised an educational exercise in which 81 transfusion services supporting obstetrics performed tube-method RhD typing on 2 unknown red blood cell challenge specimens identified as (1) maternal and (2) newborn. Both specimens were from the same weak D-reactive donor. The exercise revealed how participants responded to these different clinical situations. RESULTS.—: Of reporting laboratories, 14% (11 of 80) obtained discrepant immediate-spin reactions on the 2 specimens. Nine different reporting terms were used to interpret weak D-reactive maternal RhD types to obstetricians. In laboratories obtaining negative maternal immediate-spin reactions, 28% (16 of 57) performed unwarranted antiglobulin testing, sometimes leading to recommendations against giving RhIG. To screen for excess fetomaternal hemorrhage after a weak D-reactive newborn, 47% (34 of 73) of reporting laboratories would have employed a contraindicated fetal rosette test, risking false-negative results and inadequate RhIG coverage. Sixty percent (44 of 73) of laboratories would obtain RHD genotyping in some or all cases. CONCLUSIONS.—: For obstetric and neonatal patients with serologic weak D phenotypes, we found several critical problems in transfusion service laboratory practices. We provide recommendations for appropriate testing, consistent immunohematologic terminology, and RHD genotype-guided management of Rh immune globulin therapy and RBC transfusions.