CONTEXT.—: Syphilis, a reemerging disease caused by spirochete Treponema pallidum, is becoming more frequent in surgical pathology and hematopathology practices. Hematopathologists typically receive lymph node biopsies from patients with syphilis who have localized or diffuse lymphadenopathy. Occasionally, syphilis infection in the aerodigestive tract can show a prominent lymphoplasmacytic infiltrate and mimic lymphoma. Besides the varying and occasional atypical morphology, the fact that clinical suspicion tends to be low or absent when histologic evaluation is requested adds to the importance of making this diagnosis. OBJECTIVE.—: To summarize histologic features of syphilitic lymphadenitis and syphilis lesions in the aerodigestive tract, and to review differential diagnosis and potential diagnostic pitfalls. DATA SOURCES.—: Literature review via PubMed search. CONCLUSIONS.—: Characteristic histologic findings in syphilitic lymphadenitis include thickened capsule with plasma cell-rich inflammatory infiltrate, reactive follicular and paracortical hyperplasia with prominent lymphoplasmacytic infiltrate, and vasculitis. Lymph nodes, however, can show a number of other nonspecific histologic features, which frequently makes the diagnosis quite challenging. In the aerodigestive tract, syphilis is characterized by plasma cell-rich infiltrates. Immunohistochemistry for T pallidum is the preferred method for detecting spirochetes; however, this immunohistochemical stain shows cross-reactivity with other treponemal and commensal spirochetes. Differential diagnosis of syphilis in lymph nodes and the aerodigestive tract is broad and includes reactive, infectious, and neoplastic entities. Pathologists should be aware of the histologic features of syphilis and keep this challenging entity in the differential diagnosis.

CONTEXT.—: Immunohistochemistry plays an important role in dermatopathology, particularly for melanocytic lesions and poorly differentiated malignancies. In the field of bone and soft tissue pathology, molecular methods remain the gold standard for diagnosis; however, immunohistochemistry targeting underlying molecular alterations represents a valuable screening tool, especially in areas with limited access to molecular testing. OBJECTIVE.—: To describe the utility and limitations of new and emerging immunohistochemical stains in the diagnosis of skin, soft tissue, and bone tumors. DATA SOURCES.—: A literature review of recently described immunohistochemical stains in the fields of dermatopathology and bone and soft tissue pathology was performed. CONCLUSIONS.—: Immunohistochemistry is an important adjunctive tool for select entities in dermatopathology and bone and soft tissue pathology, and it provides pathologists with value evidence of their behavior, underlying molecular alterations, and line of differentiation. Furthermore, immunostains targeting molecular abnormalities have the potential to replace current molecular methods. Many of these recently described stains demonstrate higher sensitivity and specificity; however, limitations and pitfalls still exist, and correlation with morphologic and clinical findings remains essential for diagnosis.

CONTEXT.—: Next-generation sequencing-based approaches using RNA have increasingly been used by clinical laboratories for the detection of fusion genes, intragenic rearrangements, and exon-skipping events. Correspondingly, the College of American Pathologists (CAP) has advanced RNA sequencing proficiency testing (PT) to ensure optimal performance of these assays. OBJECTIVE.—: To report on laboratory performance and practices of RNA sequencing for the detection of fusion genes, intragenic rearrangements, and exon-skipping events using CAP PT data from 8 mailings (2018-A through 2021-B). DESIGN.—: CAP PT RNA sequencing program results from 153 laboratories across 24 proficiency test specimens, interrogating 22 distinct engineered fusion transcripts, were analyzed for correct identification of the fusion event, associated performance variables, and laboratory practices. RESULTS.—: Overall, the 4-year program detection rate (sensitivity) was 95.5% (1486 of 1556 results). False-negative rates were 3.6% (53 of 1463) and 18.3% (17 of 93) for fusion gene and intragenic rearrangement/exon-skipping events, respectively. Only 19 false-positive results were reported among the 8 PT mailings, and most were likely the result of preanalytical or postanalytical errors. There were no practice characteristics (eg, instrumentation, sequencing method) significantly associated with the fusion detection results. CONCLUSIONS.—: These data reveal a high overall sensitivity and specificity for fusion gene detection by participating laboratories using clinical RNA sequencing. Performance was comparable across all laboratories, regardless of methodology. The fraction of false-negative results for intragenic rearrangement/exon-skipping events was greater than that for the chimeric fusion genes. False-negative results could not be attributed to any specific practice characteristics.

CONTEXT.—: Social media (SM) use in pathology and medicine today is widespread, receives active advocacy, and is said to bring a host of benefits. In latter days, the harmful effects of SM have received attention, but they have yet been followed by greater encouragement of professionalized SM usage. SM use in medicine has seen adoption in parallel to its general ascendancy, even though the platforms are products with purposes misaligned with the practice of medicine. OBJECTIVE.—: To (1) characterize premises and forces that propel professional SM platform adoption and use, and (2) examine wide-ranging literature, both medical and nonmedical, that substantiates the premises and to find counteracting perspectives and evidence. DATA SOURCES.—: Review of the literature using relevant keyword searches in PubMed, Google Scholar, Dimensions, and Web of Science for articles that study/describe professional SM use in pathology and medicine. Additionally, we examined business, technology, and social sciences literature and high-quality gray literature (newspapers, books, blogs) that addressed questions in relation to the topic of professional SM adoption. CONCLUSIONS.—: We identified 6 major premises as motivators of professional SM use and highlight significant counteracting factors. We conclude that the harms of professionalized SM use have not been fully considered in the medical literature and that a change in direction and the creation of new communication platforms would be beneficial.

CONTEXT.—: Recent molecular discoveries have led to improved understanding of tumor biology and the development of new diagnostic assays. OBJECTIVE.—: To review primarily 3 examples of liver tumors and to briefly illustrate how recent molecular discoveries have altered clinical liver pathology practice. DATA SOURCES.—: First, we will discuss fibrolamellar carcinoma, which will be the main focus of discussion, as an example for new diagnostic tests that have been developed as a result of molecular discoveries. Additional information on the role of molecular diagnostics in hepatocellular adenoma and hepatocellular carcinoma will be provided. Second, we will use the example of epithelioid hemangioendothelioma as an example of how new diagnostic tools, based on molecular discoveries, may support improved prognostication. Finally, we will use the example of intrahepatic cholangiocarcinoma as an example of a liver tumor where new molecular discoveries have identified tractable therapeutic targets and led to new effective therapies. This portion of the manuscript will also include a description of the anatomic and molecular differences between intrahepatic, hilar, and extrahepatic cholangiocarcinoma. CONCLUSIONS.—: Fueled by molecular discoveries, new and better diagnostic tests and therapeutic targets have improved clinical care in patients affected by liver tumors.

CONTEXT.—: Salivary gland tumors are rare tumor types for which the molecular understanding has resulted in a rapid expansion and shuffling of entities. These changes are reflected in the 5th edition World Health Organization Classification of Head and Neck Tumours (WHO 5th edition), although many nuances still remain. OBJECTIVE.—: To review how molecular alterations have helped recategorize, justify, and reinstate entities into our lexicon as well as defining interrelationships between categories, new entities, and subtypes. Furthermore, newer theranostic applications to molecular phenotype will be summarized. DATA SOURCES.—: World Health Organization Classification of Head and Neck Tumours (WHO 3rd through 5th editions), literature review, personal and institutional experience. CONCLUSIONS.—: Molecular alterations have helped reclassify, retain, and create new categories by augmenting rather than replacing standard criteria. Key entities that have emerged include sclerosing polycystic adenoma, microsecretory adenocarcinoma, and mucinous adenocarcinoma. Molecular phenotypes solidify the range of morphology in established entities such as mucoepidermoid carcinoma and facilitate connectivity between entities. Molecular characteristics now allow for targeted therapeutic approaches for secretory carcinoma and adenoid cystic carcinoma.

CONTEXT.—: Loose tumor cells and tumor cell clusters can be recognized in the lumen of intratumoral pulmonary arteries of resected non-small cell lung cancer specimens. It is unclear whether these should be considered tumor-emboli, and as such could predict a worsened prognosis. OBJECTIVE.—: To investigate the nature and prognostic impact of pulmonary artery intraluminal tumor cells. DESIGN.—: This multicenter study involved an exploratory pilot study and a validation study from 3 institutions. For the exploratory pilot, a retrospective pulmonary resection cohort of primary adenocarcinomas, diagnosed between November 2007 and November 2010, were scored for the presence of tumor cells, as well as potentially other cells in the intravascular spaces using hematoxylin-eosin, and cytokeratin 7 (CK7) stains. In the validation part, 2 retrospective cohorts of resected pulmonary adenocarcinomas, between January 2011 and December 2016, were included. Recurrence-free survival (RFS) and overall survival (OS) data were collected. RESULTS.—: In the pilot study, CK7+ intravascular cells, mainly tumor cells, were present in 23 of 33 patients (69.7%). The 5-year OS for patients with intravascular tumor cells was 61%, compared with 40% for patients without intravascular tumor cells (P = .19). In the validation study, CK7+ intravascular tumor cells were present in 41 of 70 patients (58.6%). The 5-year RFS for patients with intravascular tumor cells was 80.0%, compared with 80.6% in patients without intravascular tumor cells (P = .52). The 5-year OS rates were, respectively, 82.8% and 71.6% (P = .16). CONCLUSIONS.—: Loose tumor cells in pulmonary arterial lumina were found in most non-small cell lung cancer resection specimens and were not associated with a worse RFS or OS. Therefore, most probably they represent an artifact.

CONTEXT.—: Droplet digital polymerase chain reaction (ddPCR) is a sensitive method to detect common pathogenic EGFR mutations in non-small cell lung cancer. Although targeted assays have not been specifically designed to detect them, uncommon EGFR mutations have been linked to response to targeted therapy. OBJECTIVE.—: To describe atypical ddPCR patterns that correspond to uncommon but clinically actionable EGFR mutations. DESIGN.—: A cohort of 1134 consecutive non-small cell lung cancers that underwent targeted next-generation sequencing was reviewed. Uncommon EGFR mutations involving probe binding sites were evaluated by ddPCR. RESULTS.—: Two hundred fifty-five of 1134 cancers (22.5%) harbored pathogenic EGFR mutations. One hundred eighty-six of 255 (72.9%) had canonical EGFR exon 19 deletion or exon 21 p.L858R variants designed for detection by ddPCR. An additional 25 of 255 cases (9.8%) had uncommon EGFR mutations within the probe-binding site, including one case with concurrent uncommon mutations in both exon 19 and exon 21. These mutations included uncommon EGFR exon 19 deletions (n = 6), EGFR exon 19 substitutions p.L747P (n = 3) and p.L747A (n = 1), dinucleotide substitutions leading to EGFR p.L858R (n = 5), EGFR exon 21 substitutions p.K860I (n = 1) and p.L861Q (n = 9), and EGFR p.[L858R;K860I] (n = 1). Droplet digital polymerase chain reaction generated atypical but reproducible signal for each of these uncommon variants. CONCLUSIONS.—: Droplet digital polymerase chain reaction analysis of uncommon pathogenic EGFR variants can yield unique and reproducible results. Recognition of atypical patterns in EGFR ddPCR testing can prompt confirmatory molecular testing and aid appropriate targeted therapy selection for patients with non-small cell lung cancer.

CONTEXT.—: Increased band neutrophils in blood smear differential counts ("bandemia") are entrenched in medicine as a flag for sepsis. However, laboratory hematology experts have long advocated for discontinuation of reporting bands separately from segmented neutrophils because of poor sensitivity and specificity, poor interobserver agreement, and availability of alternative biomarkers for sepsis. OBJECTIVE.—: To describe band neutrophil reporting practices and reproducibility of band classification among laboratories participating in the College of American Pathologists (CAP) proficiency testing (PT) program. DESIGN.—: A survey questionnaire was distributed to hematology PT participants. A subsequent morphologic challenge included 12 preselected cell identifications of segmented neutrophils, bands, and metamyelocytes, and a 100-cell manual differential count of a digitally scanned blood smear. RESULTS.—: Among laboratories that reported manual differentials, most respondents reported bands (4554 of 5268; 86.4%). Only 3222 of 4412 respondents (73.0%) provided band reference ranges. Though participants classified "easy" band neutrophils well (78.0%-98.3%), categorization of cell identifications for "moderate" and "difficult" bands was poor (3.1%-39.0% of laboratories), with classification instead as segmented neutrophils. This pattern was seen regardless of laboratory demographic characteristics. Marked variability in band counts was observed on the 100-cell differential count for both CAP PT participants and CAP Hematology and Clinical Microscopy Committee (HCMC) members (coefficients of variation, 55.8% and 32.9%, respectively). Variability was significantly improved when segmented and band neutrophils were grouped together (coefficients of variation, 6.2% and 5.0%, respectively). CONCLUSIONS.—: Most CAP PT-participating laboratories report band counts, many without reference ranges. The survey confirms significant interlaboratory variability of band enumeration when bands are separately identified from segmented neutrophils. This study reaffirms the CAP Hematology and Clinical Microscopy Committee's strong recommendation to group segmented and band neutrophils together in manual differential counts.

CONTEXT.—: To provide high-quality, safe training during the COVID-19 pandemic, our anatomic pathology fellowship program implemented a hybrid virtual/in-person training model with supplemental digital material. OBJECTIVE.—: To evaluate the impact of this model. DESIGN.—: We examined Accreditation Council for Graduate Medical Education survey results and board pass rates for fellows before the pandemic (group 1); during the pandemic peak (group 2); and early and late after the pandemic peak (groups 3 and 4). Additionally, we distributed an online survey including questions related to performance as attending physicians and fellowship experience to recent graduates. RESULTS.—: Information loss during handover, supervision and teaching by faculty, and having at least 4 free days a month exhibited the greatest score declines between group 1 and groups 2, 3, and 4 on the Accreditation Council for Graduate Medical Education surveys. No differences were seen in board passing rates between groups. The groups did not differ in responses regarding preparation for role as attending, confidence in role as attending, or overall impression of the fellowship program. The pandemic-affected groups responded more positively on the perceived utility of supplemental digital material, impact of digital pathology on quality of education, and impact of supplemental digital material on familiarity with digital pathology. The difference was particularly large between group 1 and combined groups 3 and 4. CONCLUSIONS.—: Despite the limitations noted, the hybrid training model was effective and successfully prepared fellows for their role as attending physicians. Similar studies can be informative for the implementation of similar programs or for the meaningful integration of digital pathology into training curricula.

CONTEXT.—: RNA sequencing study has demonstrated that human epidermal growth factor receptor 2 (HER2) RNA levels influence anti-HER2 therapeutic efficacy. However, in situ HER2 RNA expression (isHRE), which evaluates HER2 RNA expression in tissue, has remained unclear in breast cancers (BCs) of various HER2 immunohistochemistry (IHC)/in situ hybridization (ISH) categories. OBJECTIVE.—: To correlate isHRE with all HER2 IHC/fluorescence ISH (FISH) categories in BC. DESIGN.—: Formalin-fixed, paraffin-embedded tissue sections from 259 BCs, covering all IHC/FISH categories, were analyzed for isHRE by RNAscope. RESULTS.—: We validated HER2 RNAscope scoring as a semiquantitative method to evaluate isHRE and demonstrated significantly higher RNAscope scores in IHC 3+ than in IHC 2+ cases, and in IHC 2+ than in IHC 0/1+ cases. Among the 5 IHC 2+/FISH groups, group 1 (G1) cases had the highest scores. The scores in G3 cases were higher than those in G2, but not significantly different from those in G4 and G5. G4 cases had significantly higher scores than those in G2. Higher HER2 copy numbers and HER2:CEP 17 (centromere 17) copy number ratios were significantly correlated with higher isHRE in G1 cases, but not in G2 to G5 cases. RNAscope scores were significantly lower in HER2-negative (IHC 0) than in HER2-low (IHC 2+/FISH- and IHC 1+) BCs but were not different between IHC 0 and 1+ BCs when analyzed separately. CONCLUSIONS.—: We demonstrate the HER2 RNA expression status among BCs of various HER2 IHC/FISH categories in tissue. Such information may be relevant for anti-HER2 treatment decisions considering the role of HER2 RNA expression in predicting anti-HER2 therapeutic efficacy.

CONTEXT.—: Recent data suggest mesenteric tumor deposits (MTDs) indicate poor prognosis in small bowel well-differentiated neuroendocrine tumors (SB-NETs), including compared to positive lymph nodes, making their distinction crucial. OBJECTIVE.—: To study interobserver agreement in distinguishing SB-NET MTDs from positive nodes. DESIGN.—: Virtual slides from 36 locally metastatic SB-NET foci were shared among 7 gastrointestinal pathologists, who interpreted each as an MTD or a positive node. Observers ranked their 5 preferred choices among a supplied list of potentially useful histologic features, for both options. Diagnostic opinions were compared using Fleiss multirater and Cohen weighted κ analyses. RESULTS.—: Preferred criteria for MTD included irregular shape (n = 7, top choice for 5), perineural invasion/nerve entrapment (n = 7, top choice for 2), encased thick-walled vessels (n = 7), and prominent fibrosis (n = 6). Preferred criteria for positive nodes included peripheral lymphoid follicles (n = 6, top choice for 4), round shape (n = 7, top choice for 2), peripheral lymphocyte rim (n = 7, top choice for 1), subcapsular sinuses (n = 7), and a capsule (n = 6). Among 36 foci, 10 (28%) each were unanimously diagnosed as MTD or positive node. For 13 foci (36%), there was a diagnosis favored by most observers (5 or 6 of 7): positive node in 8, MTD in 5. Only 3 cases (8%) had a near-even (4:3) split. Overall agreement was substantial (κ = .64, P < .001). CONCLUSIONS.—: Substantial interobserver agreement exists for distinguishing SB-NET MTDs from lymph node metastases. Favored histologic criteria in making the distinction include irregular shape and nerve/vessel entrapment for MTD, and peripheral lymphocytes/lymphoid follicles and round shape for positive nodes.

CONTEXT.—: PathElective.com was created in response to the pandemic's restrictions on interactions with trainees, and since has been incorporated into many training programs worldwide, serving as a unique means of delivering high-quality pathology and laboratory medical education at multiple levels of training. OBJECTIVE.—: To analyze student usage, performance, and satisfaction to provide insight into the effectiveness of virtual education to guide curricular evolution. DESIGN.—: Squarespace (Squarespace, Inc) was used for website development and to collect website analytics. Students were assessed before and after course participation using a dual-form crossover quiz design. Quiz data were anonymous and analyzed with a paired t test to account for varying student background. A novel analysis was performed aimed at examining the attrition rate of students across multiple modules. RESULTS.—: Over the study period (May 1, 2020 to October 31, 2021), PathElective.com received 577 483 page views, 126 180 visits, 59 928 unique visitors, and 10 278 registered users who earned 15 305 certificates. A total of 7338 premodule and postmodule quiz pairs were analyzed. The overall average increase in score was 13.83% (P = .02). All but 5 of the 56 courses experienced a statistically significant increase in score. All courses received median scores of Very Satisfied/Satisfied in all 6 assessment domains. Aggregate attrition data revealed a unique, negative polynomial relationship (R2 = 0.656). CONCLUSIONS.—: PathElective.com is a free, effective means of enhancing anatomic/clinical pathology training in medical education. These analyses offer a unique perspective on the online user experience and could guide the development of future online medical education resources.

CONTEXT.—: Pleural effusions are common cytologic specimens that can be leveraged to make diagnoses of malignancy that drive appropriate patient management. However, the overlap in morphologic features of reactive mesothelial proliferations, mesotheliomas, and adenocarcinomas can create diagnostic pitfalls in the cytologic evaluation of pleural fluids. OBJECTIVE.—: To review the morphologic spectrum of benign and malignant mesothelial proliferations in pleural effusions as well as relevant clinicoradiologic contexts and ancillary tests. DATA SOURCES.—: Existing scientific and clinical literature as of January 2023. CONCLUSIONS.—: We can leverage the knowledge of several overlapping morphologic features, clinicoradiologic scenarios, and immunohistochemical studies to enhance the diagnostic accuracy of pleural effusion cytology to appropriately delineate cases of adenocarcinoma, reactive mesothelial proliferation, and mesothelioma. Earlier diagnosis through cytology, particularly in cases of mesothelioma, may positively impact patient treatment options and prognosis.

CONTEXT.—: Infection-related glomerulonephritis (IRGN) usually manifests as a proliferative immune-complex glomerulonephritis. The degree of renal dysfunction at presentation can vary. Association with histologic features on kidney biopsy remains unknown. OBJECTIVE.—: To study the correlation between renal function in IRGN at the time of biopsy and the severity of histologic features. DESIGN.—: Culture-proven IRGN cases at our facility were included and divided based on estimated glomerular filtration rate (eGFR) 15 ml/min/1.73 m2. Patients' demographic and pathologic findings were obtained from electronic medical records and kidney biopsy reports. RESULTS.—: In total, 104 cases were diagnosed with IRGN on biopsy (mean age, 55.6 ± 15.6 years; male, n = 79 [76%]; median eGFR, 14.5 mL/min/1.73 m2), and 51 of 104 showed eGFR <15 mL/min/1.73 m2. Among all the histologic features assessed, only percent tubules with red blood cell (RBC) casts showed statistical difference, being significantly higher in the lower eGFR group (P = .004). Multivariable logistic regression analysis also showed that %tubules with RBC casts were associated with lower eGFR (odds ratio, 1.12; 95% CI, 1.01-1.24; P = .01). Patients with 5% or more RBC casts (n = 31) showed a lower eGFR (P = .02) and a higher %cellular crescent (P < .001) compared with those with less than 5% RBC casts. Patients with concomitant anticoagulant therapy (n = 11) showed higher percentages of RBC casts than those without anticoagulants (P = .02). CONCLUSIONS.—: Particular attention to the extent of RBC casts on kidney biopsy is recommended in patients with IRGN because these portend worse renal dysfunction, more so in patients requiring anticoagulation (including for hemodialysis) because they are especially vulnerable to developing anticoagulant-related nephropathy.

CONTEXT.—: Gene editing-based therapies are currently in development in the areas of oncology, inherited disease, and infectious disease. These potentially life-altering therapies are derived from decades of research in both academic and industry settings that developed technologies rooted in principles and products of nature. However, with such technologic developments come many important considerations, including adverse risks, high cost, and ethical questions. OBJECTIVE.—: To educate pathologists about gene editing technologies, inform them of potential indications and risks, outline regulatory and practical issues that could affect hospital-based practice and laboratory testing, and advocate that pathologists need to be present at discussions among industry and regulators pertaining to gene editing-based therapies. DESIGN.—: A Gene Editing Workgroup, facilitated by the College of American Pathologists Personalized Health Care Committee and consisting of pathologists of various backgrounds, was convened to develop an educational paper to serve as a stimulus to increase pathologist involvement and inquiry in gene editing therapeutic and diagnostic implementation. RESULTS.—: Through multiple discussions and literature review, the workgroup identified potential gaps in pathologists' knowledge of gene editing. Additional topics that could impact pathology and laboratory medicine were also identified and summarized in order to facilitate pathologists as stakeholders in gene editing therapy administration and monitoring and potential use in diagnostics. CONCLUSIONS.—: Gene editing therapy is a complex but potentially transformative area of medicine. This article serves as an introduction to pathologists to assist them in future discussions with colleagues and potentially identify and alter pathology practices that relate to gene editing.

CONTEXT—: Gene editing-based therapies are currently in development in the areas of oncology, inherited disease, and infectious disease. These potentially life-altering therapies are derived from decades of research in both academic and industry settings that developed technologies rooted in principles and products of nature. However, with such technologic developments come many important considerations, including adverse risks, high cost, and ethical questions. OBJECTIVE—: To educate pathologists about gene editing technologies, inform them of potential indications and risks, outline regulatory and practical issues that could affect hospital-based practice and laboratory testing, and advocate that pathologists need to be present at discussions among industry and regulators pertaining to gene editing-based therapies. DESIGN—: A Gene Editing Workgroup, facilitated by the College of American Pathologists Personalized Health Care Committee and consisting of pathologists of various backgrounds, was convened to develop an educational paper to serve as a stimulus to increase pathologist involvement and inquiry in gene editing therapeutic and diagnostic implementation. RESULTS—: Through multiple discussions and literature review, the workgroup identified potential gaps in pathologists' knowledge of gene editing. Additional topics that could impact pathology and laboratory medicine were also identified and summarized in order to facilitate pathologists as stakeholders in gene editing therapy administration and monitoring and potential use in diagnostics. CONCLUSIONS—: Gene editing therapy is a complex but potentially transformative area of medicine. This article serves as an introduction to pathologists to assist them in future discussions with colleagues and potentially identify and alter pathology practices that relate to gene editing.

CONTEXT—: In recent years, several reporting systems have been developed by national and international cytopathology organizations to standardize the evaluation of specific cytopathology specimen types. OBJECTIVE—: To assess the current implementation rates, implementation methods, and barriers to implementation of commonly used nongynecologic reporting systems in cytopathology laboratories. DESIGN—: Data were analyzed from a survey developed by the committee and distributed to participants in the College of American Pathologists Nongynecologic Cytopathology Education Program mailing. RESULTS—: Nongynecologic reporting systems with the highest rate of adoption were the Bethesda System for Reporting Thyroid Cytopathology, 2nd edition (74.1%; 552 of 745); the Paris System for Reporting Urinary Cytology (53.9%; 397 of 736); and the Milan System for Reporting Salivary Gland Cytopathology (29.1%; 200 of 688). The most common reason given for not adopting a reporting system was satisfaction with a laboratory's current system. Implementation varied among laboratories with regard to which stakeholders were involved in deciding to implement a system and the amount of education provided during the implementation process. CONCLUSIONS—: The implementation of nongynecologic reporting systems in cytopathology laboratories was highly variable.

CONTEXT.—: Many studies have depended on qualitative antibody assays to investigate questions related to COVID-19 infection, vaccination, and treatment. OBJECTIVE.—: To evaluate immunoglobulin G (IgG) levels in vaccinated individuals over time and characterize limitations of qualitative and quantitative antibody assays. DESIGN.—: Longitudinal serum samples (n = 339) were collected from 72 health care workers vaccinated against COVID-19. SARS-CoV-2 IgG levels before, during, and after vaccination were measured by using a qualitative anti-spike protein IgG assay and a quantitative anti-S1 IgG assay. Assay results were compared to understand antibody dynamics related to vaccination. RESULTS.—: Qualitative testing demonstrated 100% seroconversion after the first vaccine dose, peak IgG levels after the second vaccine dose, and a progressive 50% decline during the next 8 months. Quantitative testing demonstrated that IgG levels during and after vaccination were above the analytical measurement range. CONCLUSIONS.—: Qualitative testing demonstrates expected changes in SARS-CoV-2 IgG levels related to sequential vaccine doses and time since antigen exposure. However, proportional changes in the associated numerical signals are very likely inaccurate. Adoption of standardized quantitative SARS-CoV-2 antibody testing with a broad analytical measurement range is essential to determine a correlate of protection from COVID-19 that can be scaled for widespread use.

CONTEXT.—: Total serum bilirubin (TSB) analysis is pivotal for diagnosing neonatal hyperbilirubinemia. Because of a routine change in laboratory equipment, our TSB assay changed from a diazo to a vanadate oxidase method. Upon implementation, TSB results were substantially higher in newborns than expected based on the validation. OBJECTIVE.—: To investigate the application of TSB and intermethod differences in neonates and their impact on phototherapy treatment. DESIGN.—: The diazo and vanadate methods were compared directly using neonatal and adult samples. Anonymized external quality control data were analyzed to explore interlaboratory differences among 8 commercial TSB assays. Clinical patient data were extracted from the medical records to investigate the number of newborns receiving phototherapy. RESULTS.—: The mean bias of the vanadate versus the diazo TSB method was +17.4% and +3.7% in neonatal and adult samples, respectively. External quality control data showed that the bias of commercial TSB methods compared with the reference method varied from -3.6% to +20.2%. Within-method variation ranged from 5.2% to 16.0%. After implementation of the vanadate TSB method, the number of neonates treated with phototherapy increased approximately threefold. CONCLUSIONS.—: Currently available TSB assays lack harmonization for the diagnosis of neonatal hyperbilirubinemia. Between-methods differences are substantially higher in neonatal compared with adult samples, highlighting the importance of including neonatal samples during assay validation. Close collaboration between laboratory specialists and clinicians is essential to prevent overtreatment or undertreatment upon the implementation of novel analyzers or assays. Also, harmonization of TSB assays, with an emphasis on neonatal application, is warranted.

CONTEXT.—: Automated prostate cancer detection using machine learning technology has led to speculation that pathologists will soon be replaced by algorithms. This review covers the development of machine learning algorithms and their reported effectiveness specific to prostate cancer detection and Gleason grading. OBJECTIVE.—: To examine current algorithms regarding their accuracy and classification abilities. We provide a general explanation of the technology and how it is being used in clinical practice. The challenges to the application of machine learning algorithms in clinical practice are also discussed. DATA SOURCES.—: The literature for this review was identified and collected using a systematic search. Criteria were established prior to the sorting process to effectively direct the selection of studies. A 4-point system was implemented to rank the papers according to their relevancy. For papers accepted as relevant to our metrics, all cited and citing studies were also reviewed. Studies were then categorized based on whether they implemented binary or multi-class classification methods. Data were extracted from papers that contained accuracy, area under the curve (AUC), or κ values in the context of prostate cancer detection. The results were visually summarized to present accuracy trends between classification abilities. CONCLUSIONS.—: It is more difficult to achieve high accuracy metrics for multiclassification tasks than for binary tasks. The clinical implementation of an algorithm that can assign a Gleason grade to clinical whole slide images (WSIs) remains elusive. Machine learning technology is currently not able to replace pathologists but can serve as an important safeguard against misdiagnosis.

CONTEXT.—: Antinuclear antibodies (ANAs) against certain antigens are useful for identifying autoimmune disorders. Although new solid phase-based immunoassays have been developed for evaluating ANAs, the conventional line immunoassay (LIA) is commonly used in clinical practice. OBJECTIVE.—: To compare the clinical performance of 2 newly developed methods for detecting specific ANAs with LIA. DESIGN.—: Six hundred ninety-six serum samples were collected from 559 patients with autoimmune disease (AID) and 137 controls. The samples were screened by using the LIA, digital liquid chip method (DLCM), and chemiluminescent immunoassay (CLIA) for specific ANAs. The agreement across assays and the clinical performance of each assay in diagnosing ANA-associated rheumatic diseases (AARDs) were evaluated. RESULTS.—: Perfect agreement was observed among all assays for anti-centromere protein B (κ = 0.85-0.97), anti-ribosome P (κ = 0.85-0.88), anti-SSA 52 (κ = 0.86-0.89), and anti-SSA 60 (κ = 0.89-0.91); moderate to substantial agreement was detected for the autoantibodies against Sm, Jo-1, ribonucleoprotein, Scl-70, and SSB (κ = 0.55-0.80). LIA exhibited better sensitivity for diagnosing AARDs, while DLCM and CLIA demonstrated higher specificity. In the subset of AIDs, especially systemic lupus erythematosus, antibody positive percentages varied greatly between assays. CONCLUSIONS.—: The 3 assays showed comparable qualitative agreement; however, the standardization of testing for ANAs remains challenging owing to intermanufacturer variations. Moreover, DLCM and CLIA exhibited better specificity in distinguishing non-AID individuals, whereas LIA was more sensitive in diagnosing AARDs.

CONTEXT.—: The pathologic diagnosis of pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is challenging. OBJECTIVE.—: To evaluate the diagnostic usefulness and limitations of current diagnostic strategies for pulmonary MALT lymphoma. DESIGN.—: A retrospective review of 120 cases of pulmonary MALT lymphoma from 2014 through 2021 was performed. RESULTS.—: Clinicoradiologic presentations overlapped with previous observations in those with MALT lymphoma, such as a wide age range, female predominance, frequent association with autoimmune disease or immunodeficiency, and broad imaging findings. The histopathologic diagnosis was based on a combination of morphology, immunohistochemistry, and demonstration of B-cell lineage clonality. Two-thirds (76 of 113) of MALT lymphomas had lymphoplasmacytoid cytomorphology. Occasionally, MALT lymphomas were associated with granulomas/giant cells (29%, 35 of 120) or immunoglobulin deposition disease (21%, 25 of 120), including light chain/heavy chain deposition disease, amyloidosis, and/or crystal storing histiocytosis. While CD5, CD10, Bcl-2, and Bcl-6 rarely revealed aberrancies, aberrant CD43 expression either on B-cells or on plasma cells was detected in 42% (27 of 64) of cases, including cases for which proof of clonality could not be obtained. κ/λ in situ hybridization was particularly useful for tumors with lymphoplasmacytoid morphology but performed poorly in lymphomas having no plasmacytic differentiation. κ/λ immunohistochemistry showed no additional usefulness when applied together with κ/λ in situ hybridization. Immunoglobulin gene rearrangement studies by polymerase chain reaction achieved high detection rates of clonality in all cytomorphologic subgroups. CONCLUSIONS.—: Our study offers a practical evaluation of common diagnostic tests in pulmonary MALT lymphoma. We offer recommendations for a diagnostic workup that takes into consideration the usefulness and the specific limitations of the various diagnostic strategies.

CONTEXT.—: The first case of COVID-19 in the United States was confirmed in January 2020. Initially, little was known about the epidemiology and clinical course of the disease, and diagnostic testing was limited in the United States until March/April 2020. Since then, many studies have speculated that SARS-CoV-2 may have preexisted undiagnosed outside China before the known outbreak. OBJECTIVE.—: To evaluate the prevalence of SARS-CoV-2 in adult autopsy cases performed just before and during the beginning of the pandemic at our institution, where autopsy was not performed on known COVID-19 cases. DESIGN.—: We included adult autopsies performed in our institution from June 1, 2019, to June 30, 2020. Cases were divided into groups based on the likelihood of cause of death being related to COVID-19, presence of a clinical respiratory illness, and histologic findings of pneumonia. Archived formalin-fixed, paraffin-embedded lung tissue of all COVID-possible cases and COVID-unlikely cases with pneumonia was tested for SARS-CoV-2 RNA, using Centers for Disease Control and Prevention 2019-nCoV quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). RESULTS.—: Eighty-eight cases were identified, and among those, 42 (48%) were considered COVID-possible cause of death, with 24 of those 42 cases (57%) showing respiratory illness and/or pneumonia. COVID-19 as cause of death was considered unlikely in 46 of 88 cases (52%), with 34 of those 46 cases (74%) showing no respiratory illness or pneumonia. SARS-CoV-2 real-time reverse transcription-polymerase chain reaction was performed on a total of 49 cases, 42 COVID-possible and 7 COVID-unlikely with pneumonia, and all cases were negative (0 of 49). CONCLUSIONS.—: Our data suggest that autopsied patients in our community who died between June 1, 2019, and June 30, 2020, without known COVID-19 were unlikely to have had subclinical and/or undiagnosed COVID-19 infection.