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.

MRI, clinical, and radiomic models for differentiation of uterine leiomyosarcoma and leiomyoma.

PURPOSE: To assess the predictive ability of conventional MRI features and MRI texture features in differentiating uterine leiomyoma (LM) from uterine leiomyosarcoma (LMS). METHODS: This single-center, IRB-approved, HIPAA-compliant retrospective study included 108 patients (69 LM, 39 LMS) who had pathology, preoperative MRI, and clinical data available at our tertiary academic institution. Two radiologists independently evaluated 14 features on preoperative MRI. Texture features based on 3D segmentation were extracted from T2W-weighted MRI (T2WI) using commercially available texture software (TexRAD™, Feedback Medical Ltd., Great Britain). MRI conventional features, and clinical and MRI texture features were compared between LM and LMS groups. Dataset was randomly divided into training (86 cases) and testing (22 cases) cohorts (8:2 ratio); training cohort was further subdivided into training and validation sets using ten-fold cross-validation. Optimal radiomics model was selected out of 90 different machine learning pipelines and five models containing different combinations of MRI, clinical, and radiomics variables. RESULTS: 12/14 MRI conventional features and 2/2 clinical features were significantly different between LM and LMS groups. MRI conventional features had moderate to excellent inter-reader agreement for all but two features. Models combining MRI conventional and clinical features (AUC 0.956) and MRI conventional, clinical, and radiomics features (AUC 0.989) had better performance compared to models containing MRI conventional features alone (AUC 0.846 and 0.890) or radiomics features alone (0.929). CONCLUSION: While multiple MRI and clinical features differed between LM and LMS groups, the model combining MRI, clinical, and radiomic features had the best predictive ability but was only marginally better than a model utilizing conventional MRI and clinical data alone.

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.

Endometrial Carcinomas With Subclonal Loss of Mismatch Repair Proteins: A Clinicopathologic and Genomic Study.

Subclonal loss of mismatch repair (MMR) proteins has been described in a small subset of endometrial carcinomas (ECs), but the genomic basis for this phenomenon has received limited attention. Herein, we retrospectively evaluated all ECs with MMR immunohistochemistry (n=285) for subclonal loss, and in those (n=6), performed a detailed clinicopathologic and genomic comparison of the MMR-deficient and MMR-proficient components. Three tumors were FIGO stage IA, and one each stage IB, II, and IIIC2. Patterns of subclonal loss were as follows: (1) 3 FIGO grade 1 endometrioid carcinomas with subclonal MLH1/PMS2, MLH1 promoter hypermethylation, and no MMR gene mutations; (2) POLE -mutated FIGO grade 3 endometrioid carcinoma with subclonal PMS2, and PMS2 and MSH6 mutations limited to the MMR-deficient component; (3) dedifferentiated carcinoma with subclonal MSH2/MSH6, as well as complete loss of MLH1/PMS2, MLH1 promoter hypermethylation, and PMS2 and MSH6 mutations in both components; (4) dedifferentiated carcinoma with subclonal MSH6, and somatic and germline MSH6 mutations in both components, but with a higher allele frequency in MMR-deficient foci. Recurrences occurred in 2 patients, one consisted of the MMR-proficient component from a FIGO 1 endometrioid carcinoma, while the other was from the MSH6 -mutated dedifferentiated endometrioid carcinoma. At the last follow-up (median: 44 mo), 4 patients were alive and disease-free and 2 were alive with disease. In summary, subclonal MMR loss reflects subclonal and often complex genomic and epigenetic alterations, which may have therapeutic implications and therefore must be reported when present. In addition, subclonal loss can occur in both POLE -mutated and Lynch syndrome-associated ECs.

Application of Current Pathologic Criteria for Atypical Placental Site Nodule Suggests That Refined Criteria Are Needed.

Atypical placental site nodules (APSNs) are histologically intermediate between placental site nodules (PSNs) and epithelioid trophoblastic tumors (ETTs). Little data exists to characterize these lesions and the risk of transformation from PSN to ETT. Recent World Health Organization (WHO) criteria for distinction of APSN are vague and not objectively defined. We identified cases signed out as PSN (n=33) and APSN (n=11) and aimed to characterize, statistically compare, and assess the risk of transformation in PSNs using data including size, location, mitotic rate, Ki-67 proliferation index, trophoblastic cells per high-power field, presence of severe cytologic atypia, beta-human chorionic gonadotropin levels, time since last pregnancy, presence of calcification, necrosis, or apoptosis, and follow-up results. All cases were confirmed to be positive for p63, and a Ki-67/AE1/AE3 dual stain was used to evaluate the Ki-67 proliferation index in the trophoblastic cells. In our cohort, slight changes in the interpretation of WHO criteria for PSN and APSN led to marked differences in the proportion of PSNs flagged as "atypical." There was no statistically significant difference in the persistence of APSN versus non-APSN. None of the PSNs transformed to ETT. Current criteria for distinction between PSN and APSN are largely subjective. More objective, clearly defined, and clinically meaningful criteria are needed to distinguish between PSN and APSN, thus aiding in assessing the rare risk of transformation to ETT.

Fumarate Hydratase and S-(2-Succinyl)-Cysteine Immunohistochemistry Shows Evidence of Fumarate Hydratase Deficiency in 2% of Uterine Leiomyosarcomas: A Cohort Study of 348 Tumors.

Approximately 1% to 1.5% of uterine leiomyomas are fumarate hydratase (FH)-deficient (FHd). A subset of these are associated with germline FH mutations. However, the prevalence and clinicopathologic characteristics of FHd uterine leiomyosarcoma (uLMS) remain unknown. Clinicopathologic data were collected for 348 uLMS. Morphologic features associated with FH deficiency (staghorn-type vessels, alveolar-pattern edema, macronucleoli with perinucleolar clearing, eosinophilic cytoplasmic inclusions, and chain-like nuclear arrangement) were documented. All 348 tumors were studied by FH immunohistochemistry. Eighty-nine were also studied by S-(2-succinyl)-cysteine (2SC) immunohistochemistry. Seven (2%) FHd uLMS were identified. Five showed uniformly negative FH and diffusely positive 2SC immunostaining; 1 showed variably negative to weak to strong FH and diffusely positive 2SC immunostaining; and 1 showed retained FH staining alongside positive 2SC confined to a morphologically distinct subclone. Three of 7 patients had extrauterine disease at presentation, and 3 of 6 had persistent disease or died from disease. Macronucleoli with perinucleolar clearing were significantly more common in FHd uLMS (7/7) than in uLMS with retained FH (182/341; P =0.017). Disease-specific survival, disease-free survival, and other morphologic features of FH deficiency did not differ significantly between FHd and FH-retained tumors. Our data emphasize that immunohistochemical FH deficiency does not preclude malignancy in uterine smooth muscle tumors. However, the biological significance and molecular basis of FH deficiency in uLMS, including any relationship to germline FH mutation, remain unknown, and a larger multi-institutional effort is necessary to gather sufficient FHd uLMS for more robustly powered clinicopathologic and for molecular characterization.

Dedifferentiated leiomyosarcoma of the uterus: a clinicopathologic and immunohistochemical analysis of 23 cases.

AIMS: To morphologically and immunophenotypically characterize dedifferentiated uterine leiomyosarcoma (LMS). METHODS AND RESULTS: We identified 23 dedifferentiated uterine LMS, defined as a malignant uterine smooth muscle tumour containing discrete differentiated and dedifferentiated components (i.e. with and without morphologic and immunophenotypic evidence of smooth muscle differentiation, respectively). The differentiated component was leiomyosarcoma in most cases (17/23), though some arose from a leiomyoma (n = 4) or smooth muscle tumour of uncertain malignant potential (n = 2). The dedifferentiated tumour component showed noncohesive polygonal cells with moderate to abundant cytoplasm, pleomorphic nuclei with coarse vesicular to smudged chromatin, one or more macronucleoli, frequent multinucleation, and atypical mitoses. Three cases showed heterologous osteosarcomatous or chondrosarcomatous differentiation. Immunohistochemistry revealed alterations characteristic of uterine LMS, including Rb loss (18/19); strong diffuse p16 (17/19); strong diffuse (9/19) or complete absence of (5/19) p53; and ATRX loss (6/16). Compared to a control cohort of uterine LMS without dedifferentiation, dedifferentiated uterine LMS showed significantly shorter disease-specific (median, 54 versus 20 months; 5-year DSS, 46% versus 36%; P = 0.04) and disease-free (median, 31 versus 8 months; 5-year DFS, 42% versus 8%; P = 0.002) survival. Of 19 dedifferentiated uterine LMS with follow-up, 12 had died of disease at median 14 (range, 2-73) months; four were alive with disease at 4, 12, 44, and 50 months; and three were alive with no evidence of disease at 56, 109, and 114 months. CONCLUSION: Routine prospective recognition of dedifferentiated uterine LMS and distinction from mimics is advocated for accurate prognostication and for further characterisation of these tumours.

Clinicopathologic Evaluation and Molecular Profiling of Recurrent Stage IA Endometrial Endometrioid Carcinoma: A Case-control Study.

Most low-grade, early-stage endometrial endometrioid carcinomas (EEC) have an excellent prognosis; however, recurrences occur in a small subset with several studies reporting an increase in CTNNB1 exon 3 mutations in this population. Herein we evaluated 10 recurrent low-grade (FIGO 1 or 2), early-stage (FIGO IA) EECs matched to 10 nonrecurrent EECs to further characterize their clinicopathologic features and molecular phenotype. Cases were matched to controls based on size, grade, and depth of invasion. All tumors were evaluated for specific clinicopathologic parameters followed by next-generation sequencing using a 1213 gene panel. Recurrent EECs demonstrated no significant clinicopathologic differences when compared with nonrecurrent EECs, in terms of age, body mass index, pattern of invasion, presence of endometrial atypical hyperplasia/endometrioid intraepithelial neoplasia, associated metaplastic changes, peritumoral lymphocytes, mitoses, and tumor-infiltrating lymphocytes. Both cohorts also showed a similar number of pathogenic mutations, including CTNNB1 exon 3 mutations, as well as tumor mutational burden and microsatellite profiles. Although in this particular study, the lack of correlation between CTNNB1 exon 3 mutation and recurrence might be secondary to a small sample size, it also suggests the presence of other contributing factors. Thus, it helps set the foundation for larger series incorporating whole genome, transcriptome, proteome, and epigenome analyses to answer this clinically important question.

Low-grade Fibromyxoid Sarcoma of the Vulva and Vagina: Clinical, Pathologic, and Molecular Characterization of 7 Cases and Review of the Literature.

Low-grade fibromyxoid sarcoma (LGFMS) is a malignancy with propensity for late relapse that principally affects deep soft tissues of the extremities and trunk. Its occurrence in the lower female genital tract is rare, and thus it may not be always considered in the differential diagnosis. We describe the salient features of 7 vulvovaginal LGFMS identified in the authors' consultation files. Clinical information was obtained from referring pathologists. Archival slides were reviewed, and immunohistochemistry and fluorescence in situ hybridization were performed in cases with available material. Median age was 40 years (range, 34 to 58 y). Primary sites included vulva (n=6) and vagina (n=1). Tumors were 1.2 to 8.7 cm (median, 5.0 cm) in size and grossly circumscribed with firm to focally gelatinous cut surfaces. Microscopically, 5/7 had infiltrative edges. All tumors showed fibrous and myxoid areas, with lobulated myxoid foci in 5/7, comprising storiform, patternless, or (less often) fascicular arrangement of spindled to stellate cells with bland, slender to ovoid nuclei. In all cases, mitoses were <1/2.4 mm 2 , and necrosis was absent. Capillary "arcades" were seen in 3/7. Margins were positive in 3/6. Immunohistochemistry showed positive epithelial membrane antigen in 4/6 and MUC4 in 5/6. Fluorescence in situ hybridization detected FUS rearrangement in 5/7. Both tumors without FUS rearrangement were also negative for EWSR1 rearrangement. All 5 patients with available follow-up were alive and disease-free 10 to 150 months (median, 57 mo) after diagnosis. However, a review of vulvovaginal/pelvic LGFMS previously reported shows recurrences as late as 45 years after initial diagnosis. Pathologists need to be aware that LGFMS can arise in the vulvovaginal region. Tumor lobulation, capillary arcades, and positive MUC4 are helpful features distinguishing LGFMS from other bland myxoid spindle cell neoplasms in the lower female genital tract. Molecular testing can be useful in challenging cases. Complete excision is feasible for most vulvovaginal LGFMS. Long-term surveillance is required as local and/or distant spread can occur decades after diagnosis.

Clinical and molecular validation of BAP1, MTAP, P53, and Merlin immunohistochemistry in diagnosis of pleural mesothelioma.

BAP1 and MTAP immunostains play an important role in diagnosis of mesothelioma, but additional markers are needed to increase sensitivity. We analyzed 84 pleural mesotheliomas (51 epithelioid, 27 biphasic, 6 sarcomatoid) by a hybrid-capture next-generation sequencing (NGS) panel including complete coverage of coding and splicing regions for BAP1, CDKN2A/MTAP, NF2, and TP53 and correlated molecular findings with diagnostic immunostains for BAP1, MTAP, Merlin, and p53, respectively. Fifty-seven reactive mesothelial proliferations served as benign comparators. Loss of BAP1, MTAP, and Merlin protein expression were, respectively, 54%, 46%, and 52% sensitive and 100% specific for mesothelioma. Two-marker immunopanels of BAP1 + MTAP, BAP1 + Merlin, and MTAP + Merlin were 79%, 85%, and 71% sensitive for mesothelioma, while a three-marker immunopanel of BAP1 + MTAP + Merlin was 90% sensitive. Diffuse (mutant-pattern) p53 immunostaining was seen in only 6 (7%) tumors but represented the only immunohistochemical abnormality in 2 cases. Null-pattern p53 was not specific for malignancy. An immunopanel of BAP1 + MTAP + Merlin + p53 was 93% sensitive for mesothelioma, and panel NGS detected a pathogenic alteration in BAP1, MTAP, NF2, and/or TP53 in 95%. Together, 83 (99%) of 84 tumors showed a diagnostic alteration by either immunohistochemistry or panel NGS. Adding Merlin to the standard BAP1 + MTAP immunopanel increases sensitivity for mesothelioma without sacrificing specificity. p53 immunohistochemistry and panel NGS with complete coverage of BAP1, CDKN2A/MTAP, TP53, and NF2 may be useful in diagnostically challenging cases.

Genomic catastrophe, the peritoneal cavity and ovarian cancer prevention.

The current theory of carcinogenesis for the deadliest of 'ovarian' cancers-high-grade serous carcinoma (HGSC)-holds that the malignancy develops first in the fallopian tube and spreads to the ovaries, peritoneum, and/or regional lymph nodes. This is based primarily on the observation of early forms of serous neoplasia (serous tubal intraepithelial lesions [STILs], and serous tubal intraepithelial carcinomas [STICS]) in the fimbria of women undergoing risk reduction surgery. However, these lesions are uncommon in the general population, confer a low risk (5%) of HGSC following their removal in at-risk women with germ-line BRCA1/2 mutations, and require 4 or more years to recur as intraperitoneal HGSC. These features suggest that isolated STILs and STICs behave as precursors, with uncertain cancer risk rather than carcinomas. Their evolution to HGSC within, or after, escape from the tube could proceed stepwise with multiple biologic events; however, it is unclear whether tubal or ovarian HGSCs encountered in the setting of advanced disease evolved in the same fashion. The latter scenario could also be explained by a 'catastrophic' model in which STICs suddenly develop with invasive and metastatic potential, overwhelming or obscuring the site of origin. Moreover, a similar model might explain the sudden emergence of HGSC in the peritoneal cavity following escape of precursor cells years before. Long-term follow-up data from opportunistic or prophylactic salpingectomy should shed light on where malignant transformation occurs, as well as the timeline from precursor to metastatic HGSC. © 2022 The Pathological Society of Great Britain and Ireland.

Recurrent Loss of Heterozygosity in Pancreatic Neuroendocrine Tumors.

Chromosomal aneuploidies are prognostic markers across a wide variety of tumor types, and recent literature suggests that pancreatic neuroendocrine tumors are no different. In this study 214 patients with grade 1, 2, or 3 pancreatic neuroendocrine tumors had their tissue examined for chromosomal copy number alterations using next-generation sequencing. Univariate and multivariate statistical analyses were performed with all-cause mortality and disease-specific mortality as the end comparators. As such, the cohort stratified into 3 different clinically relevant chromosomal subgroups: an indolent subgroup characterized by loss of chromosome 11 in relative isolation, an aggressive subgroup characterized by losses of chromosomes 1, 2, 3, 6, 10, 11, 16, and 22 and with no loss of chromosomes 4, 5, 7, 12, 14, 17, 19, and 20, and finally a heterogeneous third group with a subset of cases that behave even more aggressively than the aforementioned.