The Anatomic Pathology Hospitalist Model.

CONTEXT.­: Challenges to staffing a high-quality frozen section service include consolidation of health systems and pathology practices, off-campus relocation of some pathology offices, growing numbers of stand-alone surgery centers, and subspecialization among pathologists and surgeons. To address these challenges, we developed a novel anatomic pathology hospitalist model with explicit emphasis in frozen section. OBJECTIVE.­: To evaluate our anatomic pathology hospitalist program's impact on (1) frozen section staffing, (2) frozen-permanent diagnostic concordance, and (3) turnaround time. DESIGN.­: Frozen section staffing and performance data were collected for the 28-month period spanning July 1, 2021, to October 31, 2023. Outcomes were compared between hospitalists, nonhospitalists, and fellows. RESULTS.­: Hospitalists performed more frozen sections per month than nonhospitalists (median, 87 versus 17, respectively; P = .002). After implementation, nonhospitalists' average frozen section staffing obligation fell from 3.7 (30%) of 12.3 total service days per month to 2.8 (22%) of 12.6 total service days per month (P = .005), compared with hospitalists' average of 9.5 frozen section days (69%) of 13.7 total service days per month. Frozen-permanent concordance was marginally but significantly higher for hospitalists (4701 of 4744 blocks, 99.1%) than nonhospitalists (7259 of 7362 blocks, 98.6%; P = .02). Concordance did not correlate with pathologists' academic rank or subspecialization. Turnaround times were comparable for hospitalists, nonhospitalists, and fellows across multiple metrics. CONCLUSIONS.­: Our anatomic pathology hospitalists significantly reduced the frozen section obligations of nonhospitalist faculty, with a small but significant increase in frozen-permanent concordance and no substantial change in turnaround time.

Acantholytic Dyskeratoses of the Vulva: Clinicopathologic Characterization of 16 Cases and Review of the Literature.

The vulva and perineum are rarely involved by acantholytic dyskeratoses, including Hailey-Hailey disease, Darier disease, papular acantholytic dyskeratosis of the genitocrural area, acantholytic dyskeratotic acanthoma, and warty dyskeratoma. These entities show broad histomorphologic overlap, generally requiring clinical correlation for definitive classification. This institutional series aims to better characterize vulvar acantholytic dyskeratoses and provide a practical literature review and diagnostic aid for gynecologic pathologists. Our institutional archives contained 16 vulvar acantholytic dyskeratoses diagnosed between 1990 and 2023. Affected patients were 36 to 79 (mean, 58) years old and presented with one or more asymptomatic (n = 9) or pruritic (n = 6) lesions involving the vulva (predominantly the labia majora), with additional perineal involvement in 2. Four patients have known Hailey-Hailey disease. Eleven cases comprised singular, raised, erythematous, or skin-colored papules, measuring 0.2 to 0.6 (mean, 0.3) cm. Two patients had oligofocal (both with known Hailey-Hailey disease) vulvar lesions, and 2 had multifocal vulvar lesions (one with known Hailey-Hailey disease). Histologically, all showed acantholysis and dyskeratoses (abundant in 8, focal in 8, with corps ronds generally more conspicuous than corps grains). Additional features included suprabasal clefting (n = 14), dermal papillomatosis (n = 12), and acanthosis (n = 8). Adnexal involvement was rare (n = 1). No histologic features reliably distinguished sporadic versus syndromic acantholytic dyskeratoses. Sporadic lesions were cured by local excision. Patients with Hailey-Hailey disease were variably responsive to corticosteroids. Neither our series nor the literature indicate a significant correlation between sporadic or syndromic acantholytic dyskeratosis and squamous cell carcinoma. Important differential diagnoses include pemphigus vulgaris and pemphigus vegetans, for which direct immunofluorescence may be performed, when indicated.

Ewing Sarcoma of the Female Genital Tract: Clinicopathologic Analysis of 21 Cases With an Emphasis on the Differential Diagnosis of Gynecologic Round Cell, Spindle, and Epithelioid Neoplasms.

Ewing sarcoma is an uncommon neoplasm considered in the differential diagnosis of tumors with "small round cell" morphology, but its occurrence in the gynecologic tract has only been sporadically documented. Herein, we describe the largest cohort of Ewing sarcoma localized to the female genital tract to date, and emphasize their clinicopathologic resemblance to more common gynecologic neoplasms. Ewing sarcoma (n=21) was retrospectively identified from 5 institutions. The average patient age was 35 (range 6-61) years. Tumor sites included uterus (n=8), cervix (n=4), vulva (n=5), vagina (n=1), broad ligament (n=1), inguinal area (n=1), and pelvis (n=1). Nine of 18 cases in which slides were available for review demonstrated only classic round cell morphology, with the remainder showing a variable combination and prominence of variant ovoid/spindle or epithelioid appearance. Tumors showed diffuse membranous reactivity for CD99 (20/20) and were positive for NKX2.2 (8/8, diffuse) and cyclin D1 (7/7, of which 3/7 were patchy/multifocal and 4/7 were diffuse). They were negative for ER (0/6) and CD10 (0/6). Three cases were initially diagnosed as endometrial stromal sarcomas. EWSR1 rearrangement was confirmed in 20/21 by fluorescence in situ hybridization (n=15) and/or sequencing (n=8). Of the eight tumors that underwent sequencing, 6 harbored FLI1 , 1 ERG, and 1 FEV as the fusion partner. Of 11 patients with available follow-up, 5 died of disease, 1 developed lung metastases and 5 are alive with no evidence of disease. Ewing sarcoma of the gynecologic tract is a rare, aggressive entity that shares some morphologic and immunohistochemical features with other more common gynecologic neoplasms. In addition to the typical round cell appearance, variant spindled/ovoid to epithelioid morphology may also be observed and should prompt consideration of this entity with appropriate immunohistochemical and/or molecular studies.

Genomic Catastrophe (Chromothripsis and Polyploidy) Correlates With Tumor Distribution in Extrauterine High-grade Serous Carcinoma.

Most extrauterine high-grade serous carcinomas (HGSCs) are thought to develop first in the distal fallopian tube. Most models of HGSC assume origin from relatively stable, noninvasive serous tubal intraepithelial carcinomas. However, widespread tumor involvement in the absence of a serous tubal intraepithelial carcinoma could occur after catastrophic genomic events (CGEs; such as chromothripsis or polyploidy). Twenty-six HGSCs assigned to fallopian tube (n = 9, group 1) and/or ovary (n = 9, group 2), and primary peritoneal (n = 8, group 3) were assessed by microarray (Oncoscan). CGEs were identified in 15/26 (57.7%); chromothripsis-like pattern in 13/26 (50.0%) and polyploidy in 6/26 (23.1%). CGE was seen in 4/9 (44.4%), 9/9 (100%), and 2/8 (25%) cases in groups 1. 2, and 3, respectively. Overall, CGEs were seen in 9/9 (100%) cases with grossly evident ovarian parenchymal involvement versus 6/17 (35.3%) without ( P = 0.0024). Ovarian size (measured on the long axis) correlated with CGE positivity ( P = 0.016). CGEs are significantly more common in HGSCs with ovarian parenchymal involvement compared with those limited to the fallopian tube and/or extraovarian tissues. These associations suggest geographically different tumor growth patterns and support the subdivision of HGSCs according to not only the stage but also tumor distribution. They have implications for clinical and pathologic presentation, trajectory of tumor evolution, and in the case of primary peritoneal HGSCs, potentially unique precursors to tumor transitions that could inform or influence cancer prevention efforts.

Guidelines for Pathologic Diagnosis of Mesothelioma.

CONTEXT.­: Mesothelioma is an uncommon tumor that can be difficult to diagnose. OBJECTIVE.­: To provide updated, practical guidelines for the pathologic diagnosis of mesothelioma. DATA SOURCES.­: Pathologists involved in the International Mesothelioma Interest Group and others with expertise in mesothelioma contributed to this update. Reference material includes peer-reviewed publications and textbooks. CONCLUSIONS.­: There was consensus opinion regarding guidelines for (1) histomorphologic diagnosis of mesothelial tumors, including distinction of epithelioid, biphasic, and sarcomatoid mesothelioma; recognition of morphologic variants and patterns; and recognition of common morphologic pitfalls; (2) molecular pathogenesis of mesothelioma; (3) application of immunohistochemical markers to establish mesothelial lineage and distinguish mesothelioma from common morphologic differentials; (4) application of ancillary studies to distinguish benign from malignant mesothelial proliferations, including BAP1 and MTAP immunostains; novel immunomarkers such as Merlin and p53; fluorescence in situ hybridization (FISH) for homozygous deletion of CDKN2A; and novel molecular assays; (5) practical recommendations for routine reporting of mesothelioma, including grading epithelioid mesothelioma and other prognostic parameters; (6) diagnosis of mesothelioma in situ; (7) cytologic diagnosis of mesothelioma, including use of immunostains and molecular assays; and (8) features of nonmalignant peritoneal mesothelial lesions.

Outcome-Based Risk Stratification Model for the Diagnosis of Placental Maternal Vascular Malperfusion.

The Amsterdam Consensus Statement introduced the term maternal vascular malperfusion (MVM) to group a constellation of findings associated with impaired maternal-placental circulation. In isolation, these findings are relatively common in placentas from normal gestations, and there is uncertainty on how many, and which, are required. We aimed to determine the criteria essential for MVM diagnosis in correlation with obstetrical outcomes. A total of 200 placentas (100 with a reported diagnosis of MVM and 100 controls matched by maternal age and gravida-para-abortus status) were reviewed to document MVM features. Obstetrical outcomes in the current pregnancy were recorded including hypertension, pre-eclampsia with or without severe features, gestational diabetes, prematurity, fetal growth restriction, and intrauterine fetal demise. On univariate logistic regression analysis, adverse outcome was associated with low placental weight (LPW, <10% percentile for gestational age), accelerated villous maturation (AVM), decidual arteriopathy (DA), infarcts (presence and volume), distal villous hypoplasia, and excess multinucleated trophoblast in basal plate ≥2 mm (all P < .01) but not with retroplacental hemorrhage. In a multivariable model DA, infarcts and AVM were significantly associated with adverse outcomes, whereas LPW showed a trend toward significance. A receiver-operating characteristic curve including these 4 parameters showed good predictive ability (area under the curve [AUC], 0.8256). Based on the probability of an adverse outcome, we recommend consistent reporting of DA, AVM, infarcts, and LPW, summarizing them as "diagnostic of MVM" (DA or AVM plus any other feature, yielding a probability of 65%-97% for adverse obstetrical outcomes) or "suggestive of MVM" (if only 1 feature is present, or only 2 features are infarcts plus LPW, yielding a probability of up to 52%). Other features such as distal villous hypoplasia, excess (≥2 mm) multinucleated trophoblast, and retroplacental hemorrhage can also be reported, and their role in MVM diagnosis should be further studied.

Herpes Pseudotumor Mimicking Cervical Cancer With Lymph Node Metastasis in an Immunocompetent Patient.

Anogenital herpes simplex virus (HSV) infection can rarely manifest as a pseudotumor, which some have termed "hypertrophic herpes." Almost all cases are in immunocompromised patients, typically with human immunodeficiency virus/acquired immune deficiency syndrome. This presentation often mimics malignancy clinically. We present a case of cervical HSV pseudotumor with associated lymphadenopathy in an immunocompetent woman, mimicking locally advanced cervical cancer. The lesion resolved with acyclovir therapy. We emphasize that (1) clinically suspected malignancy must be confirmed by pathologic examination; (2) infectious mimics must be considered when microscopic examination fails to confirm a clinically suspected anogenital malignancy, particularly in patients with compromised or unknown immune status; (3) morphologic hallmarks of infection may be focal; (4) co-infection with multiple sexually transmitted infections can occur, particularly in immunocompromised patients, and HSV or other infection does not per se exclude concurrent human papillomavirus-associated neoplasia; and (5) anogenital HSV pseudotumor should prompt clinical evaluation for human immunodeficiency virus or other immunosuppression.

Localized Endometrial Proliferations of Pregnancy are Clonal Glandular Outgrowths Characterized by PTEN Loss and PIK3CA Pathogenic Variants.

Gestational endometrium can demonstrate a spectrum of atypical but benign changes. One such lesion is localized endometrial proliferation of pregnancy (LEPP), first described in a series of 11 cases. To understand its biological and clinical importance, we explore the pathologic, immunophenotypic, and molecular features of this entity. Nine cases of LEPP identified in 15 years were retrieved from departmental archives and reviewed. Immunohistochemistry and next-generation sequencing using a comprehensive 446-gene panel were performed when the material was available. Eight cases were identified in curettage specimens performed after first-trimester pregnancy loss, and 1 in the basal plate of a mature placenta. The mean patient age was 35 (range 27-41) years. The mean lesion size was 6.3 (range 2-12) mm. Architectural patterns, often coexisting in the same case, included cribriform (n = 7), solid (n = 5), villoglandular (n = 2), papillary (n = 2), and micropapillary (n = 1). Cytologic atypia was mild in 7 cases and moderate in 2. Mitotic activity was low (up to 3 per 2.4 mm2). All lesions were associated with neutrophils. Background Arias-Stella phenomenon was present in 4 cases. Immunohistochemistry was performed in 7 LEPP, all of which demonstrated wildtype p53, retained MSH6 and PMS2, membranous beta-catenin, and positive estrogen receptor (mean 71%) and progesterone receptor (mean 74%). All were negative for p40 except 1 case (focal weak positivity). PTEN was markedly reduced in background secretory glands in all cases; in 5/7, LEPP foci showed a complete absence of PTEN expression. PIK3CA pathogenic variants were identified in 4/4 cases sequenced; 3/4 had inactivating PTEN mutations. Follow-up, available in 8 patients (mean length = 51 months, range 7-161), was conservative with observation only and showed no persistence or adverse outcomes. LEPP is characterized by intraglandular cribriform/solid architecture, positive estrogen receptor/progesterone receptor, PTEN loss, and PIK3CA and PTEN mutations. Although our findings indicate that LEPP is neoplastic, for now, we advise against diagnosing LEPP as endometrial carcinoma or hyperplasia because LEPP has a particular clinicopathologic context (concurrent gestation), distinct morphology (purely intraepithelial complex growth), and indolent outcome. Thus, it should be distinguished from endometrial intraepithelial neoplasia and carcinoma for which therapeutic interventions are indicated.