Atypical placental site nodules: Clinicopathologic features, management and patient outcomes in an institutional series.

OBJECTIVE: To report the New England Trophoblastic Disease Center (NETDC) experience with atypical placental site nodules (APSN). METHODS: The NETDC registry was reviewed from 2005 to 2022 and clinical data abstracted. Expert pathologists in GTD reviewed available slides with concurrent immunohistochemical analysis. Targeted deep sequencing was performed for four cases. RESULTS: Among 35 cases of APSN identified, 29 had clinical and demographic data available. Abnormal uterine bleeding (59.3%) was the most common presenting symptom. Most women (79.3%) had an antecedent live birth. Two cases were incidentally diagnosed after hysterectomy for other indications, and one case lost to follow-up. Among the remaining 26 cases, 11 (42.3%) opted for hysterectomy and 15 for re-sampling (57.7%), among whom 3 later underwent hysterectomy for persistent APSN. Subsequent obstetrical outcomes included 3 spontaneous abortions, 1 therapeutic abortion, 1 ectopic pregnancy, 2 cesarean sections, 1 cesarean hysterectomy, and 1 spontaneous vaginal delivery. Subsequent pathology was available for 26 cases: 4 epithelioid trophoblastic tumors (15.4%), 9 APSN (34.6%), 3 PSN (11.5%), and 10 without abnormalities (38.4%). Histopathologic characteristics of APSN included moderate to severe cytologic atypia, median Ki-67 proliferation index of 8%, and typical immunohistochemical profiles (diffuse or multifocal positivity for p63 and GATA-3 and absent or focal CD146). No histopathologic feature predicted ETT. Among 4 sequenced cases, no recurrent genomic features were identified. CONCLUSIONS: APSN is a rare form of gestational trophoblastic proliferation with uncertain malignant potential. While normal obstetric outcomes are possible, the persistence rate is high, and definitive management remains hysterectomy.

Lesions sub-diagnostic of endometrioid intra-epithelial neoplasia/atypical hyperplasia: value of morphology and immunohistochemistry in predicting neoplastic outcome.

AIMS: Areas of gland crowding that do not fulfil diagnostic criteria of endometrioid intra-epithelial neoplasia (EIN) are often encountered in endometrial biopsies. In this study, we document the prevalence of neoplastic outcome in patients with these subdiagnostic lesions (SL) and assess the utility of morphological features and a three-marker immunohistochemistry panel (PAX2, PTEN, beta-catenin) to predict outcome. METHODS AND RESULTS: Of 430 women with SL on endometrial sampling at Brigham and Women's Hospital between 2001 and 2021 with available follow-up biopsy, 72 (17%) had a neoplastic outcome (EIN or endometrioid carcinoma). Multilayered epithelium and mitoses in SL were statistically associated with a neoplastic outcome. Abnormal three-marker staining was observed in 93% (53 of 57) of SL with neoplastic outcome and 60% (37 of 62) of a control group with benign outcome. Among the 72 patients with neoplastic outcome, EIN/carcinoma tissue was available in 33; of these, 30 (91%) showed abnormal staining for one or more markers. Remarkably, in 84% of these cases the EIN/carcinoma had the aberrant expression seen in the preceding SL. Based on a prevalence of 17%, the positive and negative predictive values of abnormal staining in one or more markers were 24 and 97%, respectively. CONCLUSIONS: The presence of SL warrants clinical surveillance and repeat sampling because it is followed by endometrioid neoplasia in a significant subset of patients. Normal three-marker staining identifies women with a very low risk of neoplastic outcome. Conversely, abnormal staining is frequent in SL with benign outcome leading to poor specificity and positive predictive value.

Gynecologic Pathology Journal Club: A 2-year, Worldwide Virtual Learning Experience With a Focus on Mentorship and Inclusion.

Journal clubs (JCs) are a common format used in teaching institutions to promote trainee engagement and develop skills in seeking out evidence-based medicine and critically evaluating literature. Digital technology has made JC accessible to worldwide audiences, which allows for increased inclusion of globally diverse presenters and attendees. Herein we describe the experience of the first 2 years of a virtual gynecologic pathology JC designed with the goal of providing mentorship and increasing inclusivity. JC began in a virtual format in April 2020 in response to the need for remote learning during the coronavirus disease 2019 pandemic. Each JC had 1 moderator, lasted 1 hour, featured up to 3 trainees/early-career pathologists, and covered articles on gynecologic surgical pathology/cytopathology. Trainees were recruited through direct contact with moderators and advertising through social media (eg, Twitter). A template was used for all presentations, and before presenting, live practice sessions were conducted with the moderator providing constructive feedback and evaluations were provided to presenters and attendees for feedback. Recordings of the meetings were made publicly available after the event through YouTube, a society website, and emails to registrants. Fifty-nine presenters participated, covering 71 articles. Most were trainees (53/59; 89%) from North America (33/59; 56%), with additional presenters from Asia (14/59; 24%), Australia/Oceania (5/59; 8%), Africa (4/59; 7%), and Europe (3/59; 5%). An average of 20 hours were spent per month by moderators on the selection of papers, meeting preparation, and provision of mentorship/feedback. Live events had a total of 827 attendees, and 16,138 interactions with the recordings were noted. Among those who self-identified on provided surveys, the attendees were most commonly from Europe (107/290; 37%) and were overwhelmingly practicing pathologists (275/341; 81%). The experience, including mentorship, format, and content, was positively reviewed by attendees and presenters. Virtual JC is an inclusive educational opportunity to engage trainees and early-career pathologists from around the world. The format allowed for the JC to be widely viewed by attendees from multiple countries, most being practicing pathologists. Based on feedback received, virtual JC appears to expand the medical knowledge of the attendees and empower presenters to develop their expertise and communication skills.

A case of placental site trophoblastic tumor managed in a low resource setting.

Placental trophoblastic site tumor (PSTT) is a rare type of gestational trophoblastic neoplasia (GTN). PSTT has a higher mortality than other types of gestational trophoblastic disease (GTD), with a rate of 16.1%, due to its relatively unpredictable behavior and reduced response to chemotherapy. Its diagnostic and management are very challenging in Low resources settings particularity in Haiti where MRI, PET Scan and IHC are not available. Further, the follow-up is very difficult because of social, political, and economic issues limiting the capacity of our patients to be present at all scheduled visits. No case of PSTT has been publicly described yet the Haitian experience in the literature in the management of such case compared to the developed world. We present a case of PSTT successfully diagnosed and managed at Mirebalais University Hospital (MUH) in Haiti with the support of telepathology and intentional partners while highlighting the difference that we observed compare to the developed world.

Macroscopic examination of gynaecological specimens: a critial and often underemphasised aspect of pathological reporting.

Pathological examination of surgical specimens and compilation of a surgical pathology report comprises a series of events which includes macroscopic examination and tissue sampling, either complete or selected. This step is critical but often overlooked in the literature and not given the attention it deserves. In this review, we discuss the macroscopic examination and grossing of gynaecological pathology specimens, with reference to national and international protocols. We provide guidance as to the degree of sampling necessary in different scenarios and stress that a common-sense approach is necessary with flexibility in the degree of sampling depending on a variety of factors.

Diagnosis of verruciform acanthotic vulvar intra-epithelial neoplasia (vaVIN) using CK17, SOX2 and GATA3 immunohistochemistry.

AIMS: Verruciform acanthotic vulvar intra-epithelial neoplasia (vaVIN) is an HPV-independent, p53 wild-type lesion with distinct morphology and documented risk of recurrence and cancer progression. vaVIN is rare, and prospective distinction from non-neoplastic hyperplastic lesions can be difficult. CK17, SOX2 and GATA3 immunohistochemistry has emerging value in the diagnosis of HPV-independent lesions, particularly differentiated VIN. We aimed to test the combined value of these markers in the diagnosis of vaVIN versus its non-neoplastic differentials in the vulva. METHODS AND RESULTS: CK17, SOX2 and GATA3 immunohistochemistry was evaluated on 16 vaVINs and 34 mimickers (verruciform xanthoma, lichen simplex chronicus, lichen sclerosus, psoriasis, pseudo-epitheliomatous hyperplasia). CK17 was scored as 3+ = full-thickness, 2+ = partial-thickness, 1+ = patchy, 0 = absent; SOX2 as 3+ = strong staining ≥ 10% cells, 2+ = moderate, 1 + =weak, 0 = staining in < 10% cells; and GATA3 as pattern 0 = loss in < 25% basal cells, 1 = loss in 25-75% basal cells, 2 = loss in > 75% basal cells. For analysis, results were recorded as positive (CK17 = 3+, SOX2 = 3+, GATA3 = patterns 1/2) or negative (CK17 = 2+/1+/0, SOX2 = 2+/1+/0, GATA3 = pattern 0). CK17, SOX2 and GATA3 positivity was documented in 81, 75 and 58% vaVINs, respectively, versus 32, 17 and 22% of non-neoplastic mimickers, respectively; ≥ 2 marker positivity conferred 83 sensitivity, 88 specificity and 86% accuracy in vaVIN diagnosis. Compared to vaVIN, SOX2 and GATA3 were differentially expressed in lichen sclerosus, lichen simplex chronicus and pseudo-epitheliomatous hyperplasia, whereas CK17 was differentially expressed in verruciform xanthoma and adjacent normal mucosa. CONCLUSIONS: CK17, SOX2 and GATA3 can be useful in the diagnosis of vaVIN and its distinction from hyperplastic non-neoplastic vulvar lesions. Although CK17 has higher sensitivity, SOX2 and GATA3 are more specific, and the combination of all markers shows optimal diagnostic accuracy.

Placenta Accreta Spectrum: Evaluation of classic and non-classic presentations, pathologic grading, and uterine scar dehiscence features in a modern institutional series.

INTRODUCTION: The aim of this study is to document the distribution of classic versus non-classic presentation of Placenta Accreta Spectrum (PAS) disorders as well as grading categories by the Society for Pediatric Pathology (SPP) and FIGO systems in an institutional cohort of gravid hysterectomies. We also document the prevalence of uterine scar as a histologic correlate for uterine scar dehiscence, a phenomenon raised by some as central to PAS pathogenesis. METHODS: PAS cases were assigned grade and designated as classic (anterior lower uterine segment implantation, prior C-section) or non-classic (implantation away from anterior lower uterine segment and/or no prior C-section). Features of dehiscence (uterine window, histologic evidence of scar) were recorded. RESULTS: Sixty-two patients were included: 76 % had prior C-section; 55 % had other forms of uterine instrumentation. Classic PAS was recorded in 52 % patients; notably, 48 % had non-classic presentation; of these, all but one had prior instrumentation (curettage, myomectomy, laparoscopy). Uterine window was described in 53 % classic and 23 % non-classic PAS. Scar was demonstrated in 31 % classic and 23 % non-classic PAS; trichrome/reticulin stains were confirmatory. 32 % cases were SPP grade 1, 18 % grade 2, 18 % grade 3a and 32 % grade 3d. Grade 3 was significantly more common in classic (72 %) than non-classic (27 %) PAS. DISCUSSION: While most PAS patients have classic presentation, a large subset does not; in addition, scar tissue is not identified histologically in most PAS hysterectomies; in these settings, PAS cannot be fully attributed to scar dehiscence. Uterine instrumentation often precedes non-classic PAS reinforcing the concept of decidual disruption as central to PAS pathogenesis. PAS grading as defined correlates with presentation (classic vs non-classic).

Pattern A endocervical adenocarcinomas with ovarian metastasis are indolent and molecularly distinct from destructively invasive adenocarcinomas.

AIMS: The invasive pattern in HPV-associated endocervical adenocarcinoma (HPVA) has prognostic value. Non-destructive (pattern A) HPVA has excellent prognosis mirroring adenocarcinoma in-situ (AIS). However, the rare occurrence of ovarian spread in these tumours suggests aggressiveness in a subset of patients with these otherwise indolent lesions. We hypothesise that AIS/pattern A HPVA with ovarian metastases are biologically different than metastatic destructively invasive HPVA. METHODS AND RESULTS: Samples from patients with HPVA and synchronous or metachronous metastases were retrieved and reviewed to confirm diagnosis and determine the Silva pattern in the primary lesion. For each case, normal tissue, cervical tumour and at least one metastasis underwent comprehensive sequencing using a 447-gene panel. Pathogenic single-nucleotide variants and segmental copy-number alterations (CNA), tumour mutational burden and molecular signatures were evaluated and compared between primary and metastases and among invasive pattern categories. We identified 13 patients: four had AIS/pattern A primaries, while nine had pattern B/C tumours. All AIS/pattern A lesions had metastasis only to ovary; 50% of patients with ovarian involvement, regardless of invasive pattern, also had involvement of the endometrium and/or fallopian tube mucosa by HPVA. In the ovary, AIS/pattern A HPVA showed deceptive well-differentiated glands, often with adenofibroma-like appearance. Conversely, pattern C HPVAs consistently showed overt infiltrative features in the ovary. Sequencing confirmed the genetic relationship between primary and metastatic tumours in each case. PIK3CA alterations were identified in three of four AIS/pattern A HPVAs and three of eight pattern B/C tumours with sequenced metastases. Pattern C tumours showed a notably higher number of CNA in primary tumours compared to pattern A/B tumours. Only one metastatic AIS/pattern A HPVA had a novel pathogenic variant compared to the primary. Conversely, five of eight pattern B/C tumours with sequenced metastases developed novel pathogenic variants in the metastasis not seen in the primary. All four AIS/pattern A patients were alive and free of disease at 31, 47, 58 and 212 months after initial diagnosis. Conversely, cancer-related death was documented in five of nine pattern B/C patients with follow-up at 7, 20, 20, 43 and 87 months. CONCLUSION: Morphologically and genomically, AIS/pattern A HPVA with secondary ovarian involvement appears distinct from destructively invasive tumours. In at least a subset of these cases, ovarian spread appears to occur via trans-Mullerian superficial extension, different from the stromal and lymphatic vascular spread typical of more aggressive tumours (pattern C). These differences may explain the indolent outcome observed in the rare subset of patients with AIS/pattern A HPVA and ovarian metastasis. Our data underscore the potential for conservative surgical management approaches to pattern A HPVA.

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.

Atypical Endometriosis: Comprehensive Characterization of Clinicopathologic, Immunohistochemical, and Molecular Features.

Atypical endometriosis (A-EMS), defined by cytologic atypia and/or crowded glands resembling endometrial intraepithelial neoplasia, remains poorly understood. We aimed to refine the morphologic, immunohistochemical, and molecular features of A-EMS in an institutional series. Cases were identified through a structured search and reviewed by 2 pathologists. Immunohistochemistry and comprehensive sequencing using a panel 447-gene coverage were performed in suitable cases. A-EMS with synchronous and/or subsequent EMS-related neoplasia were compared with those without. Of 4598 EMS cases over an 11-yr period, 36 A-EMS were identified. The mean age at presentation was 46 (range 26-68) yr. Locations included the ovary (24, 66%), tubo-ovary (6, 17%), fallopian tube (3, 8%), and peritoneum (3, 8%). The mean size was 6.5 (range 0.5-40) mm. Cytologic atypia was mild in 4 (11%), moderate in 21 (58%), and severe in 11 (31%). Most lesions were partially or completely flat (28, 78%); of these, 66% showed hobnail nuclei. Crowded/cribriform and micropapillary/papillary patterns were seen in 11 (31%) and 16 (44%) A-EMS, respectively. Immunohistochemistry, performed in 33 A-EMS, showed wildtype p53 (100%) retained PMS2/MSH6 (100%), and positive estrogen receptor (97%, mean 65% cells), progesterone receptor (76%, mean 30% cells), and Napsin A (39%). Ki67 labelling was <1% to 10% (median 5%). Nine (25%) patients presented with concurrent or subsequent ipsilateral endometrioid, seromucinous, or clear cell neoplasia (4 borderline tumors and 4 carcinomas). The only A-EMS feature statistically more frequent in this subset was crowded/glands (6/9 vs. 2/27 A-EMS without, P =0.001 Fisher exact test). Sequencing showed pathogenic variants in 5 of 6 cases analyzed, involving ATM , BRCA2 , KRAS , AKT , CTNNB1 , PTEN , and ARID1A among other genes. In 2 cases, synchronous neoplasia showed an accumulation of additional variants. A-EMS is characterized by cytologic atypia and crowded architecture but low proliferation index, positive estrogen receptor, and normal p53 and MMR, which can be helpful in the distinction from malignancy. The prevalence of synchronous/subsequent tubo-ovarian neoplasia in our series was 25%, significantly higher than the reported 1% in conventional EMS. Moreover, A-EMS harbors genomic alterations seen in EMS-related tumors and shares pathogenic variants with synchronous ipsilateral neoplasia. Therefore, it is important to report A-EMS as currently defined and describe its architectural features, especially gland crowding as this appears to increase the risk of EMS-related epithelial neoplasia. Napsin-A is often positive in A-EMS and should be interpreted with caution.

FIGO 2023 endometrial cancer staging: too much, too soon?

An updated International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial carcinoma was introduced in June 2023. The new system represents a significant departure from traditional endometrial and other gynecological carcinoma staging systems which are agnostic of parameters such as tumor type, tumor grade, lymphovascular space invasion, and molecular alterations. The updated system, which incorporates all of these 'non-anatomical' parameters, is an attempt to make staging more personalized and relevant to patient prognostication and management, and to align with the European Society of Gynaecological Oncology/European Society for Radiotherapy and Oncology/European Society of Pathology (ESGO/ESTRO/ESP) risk stratification. Herein, we present a critical review of the new staging system and discuss its advantages and disadvantages. The authors propose that the new FIGO staging system should be first appraised at a multi-institutional and global level with the input of all relevant societies (gynecology, pathology, gynecologic oncology, medical oncology, radiation oncology) to understand the impact, scope, and supporting evidence of the proposed changes. Such a process is fundamental to produce a robust system that pathologists and treating clinicians can adopt.

FOXL2: a gene central to ovarian function.

The FOXL2 (forkhead box L2) gene is located on chromosome 3 and encodes for forkhead box (FOX) family of transcription factors which play a critical role in various biological processes. Germline FOXL2 mutations have been identified in blepharophimosis/ptosis/epicanthus inversus syndrome. The somatic missense mutation in FOXL2 (FOXL2 C134W) is now known to be the defining molecular feature of adult-type granulosa cell tumour of the ovary, present in over 90% of cases of this tumour type. Immunohistochemistry for FOXL2 is used as a marker of sex cord-stromal differentiation. However, expression is not restricted to lesions harbouring FOXL2 mutations, and it is positive in a variety of sex cord-stromal proliferations other than adult-type granulosa cell tumour.

Vulvar leiomyosarcoma: A case report.

Vulvar leiomyosarcoma is a rare malignant smooth muscle tumor and the most common type of vulvar sarcoma. It can mimic benign tumors, and misdiagnosis may delay appropriate treatment. A 35-year-old woman presented to the outpatient gynecology clinic at the Mirebalais Teaching Hospital for a right vulvar mass. A complete excision of the mass was performed. Histopathology with immunohistochemistry demonstrated leiomyosarcoma. We describe the contextual challenges that ultimately compromised her care, highlighting the challenges to safe delivery of cancer care in our setting.

STK11 Adnexal Tumor in an Adolescent Female: Diagnostic Pitfalls of a Recently Described Entity.

STK11 adnexal tumor is a recently described entity with less than 25 cases reported to date. These aggressive tumors typically occur in paratubal/paraovarian soft tissues, have characteristically striking morphologic and immunohistochemical heterogeneity, and harbor pathognomonic alterations in STK11. These occur almost exclusively in adult patients, with only one reported in a pediatric patient (to our knowledge). A previously healthy 16-year-old female presented with acute abdominal pain. Imaging studies revealed large bilateral solid and cystic adnexal masses, ascites, and peritoneal nodules. Following frozen section evaluation of a left ovarian surface nodule, bilateral salpingo-oophorectomy and tumor debulking were performed. Histologically, the tumor demonstrated distinctively variable cytoarchitecture, myxoid stroma, and mixed immunophenotype. A next generation sequencing-based assay identified a pathogenic STK11 mutation. We report the youngest patient to date with an STK11 adnexal tumor, highlighting key clinicopathologic and molecular features in order to contrast them with those of other pediatric intra-abdominal malignancies. This rare and unfamiliar tumor poses a considerable diagnostic challenge and requires a multidisciplinary integrated approach to diagnosis.

Placental lesions attributed to shallow implantation, excess extravillous trophoblast and decidual hypoxia: Correlation with maternal vascular malperfusion and related obstetric conditions.

INTRODUCTION: Maternal vascular malperfusion (MVM) is one of four main patterns of placental injury defined by the Amsterdam consensus statement and is associated with adverse fetal and maternal outcomes. Laminar decidual necrosis (DLN), extravillous trophoblast islands (ETIs), placental septa (PS), and basal plate multinucleate implantation-type trophoblasts (MNTs) are lesions attributed to decidual hypoxia, excess trophoblast, and shallow implantation, but are not included in the current MVM diagnostic criteria. We aimed to investigate the relationship between these lesions and MVM. METHODS: A case-control model was used to evaluate for DLN, ETIs, PS, and MNTs. Placentas with MVM on pathologic examination (defined as ≥2 related lesions) constituted the case group, and maternal age- and GPA-status-matched placentas with less than 2 lesions constituted the control group. MVM-related obstetric morbidities were recorded, including hypertension, preeclampsia, and diabetes. These were correlated with the lesions of interest. RESULTS: 200 placentas were reviewed: 100 MVM cases and 100 controls. MNTs and PS showed significant enrichment in the MVM group (p < .05). Furthermore, larger foci of MNTs (>2 mm linear extent) were significantly associated with chronic or gestational hypertension (OR = 4.10; p < .05) and preeclampsia (OR = 8.14; p < .05). DLN extent correlated with placental infarction, but DLN and ETIs (including size and number) lacked association with MVM-related clinical conditions. DISCUSSION: As a marker of abnormally shallow placentation and related maternal morbidities, MNT merits inclusion within the MVM pathologic spectrum. Consistent reporting of MNTs >2 mm in size is recommended, as these lesions correlate with other MVM lesions and MVM-predisposing morbidities. Other lesions, particularly DLN and ETI, lacked such association questioning their diagnostic utility.

Safety of fertility sparing management in invasive mucinous ovarian carcinoma.

BACKGROUND: The aim of the study was to evaluate the safety of fertility-sparing surgery in invasive mucinous ovarian carcinomas (MOC). METHODS: Retrospective review was performed of MOCs diagnosed between 1999 and 2019 at two tertiary cancer centers. Pathology was reviewed to rule out metastasis from gastrointestinal tract. The demographics and survival outcomes were compared between women who underwent fertility-sparing surgery and those who underwent radical surgery (at least hysterectomy, bilateral salpingo-oophorectomy +/- staging). Cox proportional hazard models were constructed to evaluate the effect of fertility sparing surgery on survival. RESULTS: Of 134 with stage I disease, 42 (31%) underwent fertility-sparing surgery with unilateral salpingo-oophorectomy. Compared to women who underwent radical surgery, these women were younger with low grade, early-stage disease. Two patients (5%) in the fertility-sparing cohort experienced a recurrence and 1 of these 2 patients died due to disease progression. There was no difference in either OS or RFS between those that underwent fertility-sparing surgery and radical surgery. In a multivariable analysis adjusting for age and use of adjuvant chemotherapy, fertility-sparing surgery was not significantly associated with OS (HR 0.18; 95% CI 0.01-2.78) or RFS (HR 0.19; 95% CI 0.03-1.45). There were 4 patients (9%) with documented full-term delivery with median interval to conception of 11 months. CONCLUSIONS: Fertility-sparing surgery in stage I MOC is not associated with worse outcomes compared to radical surgery and is reasonable to offer to those with early stage disease who wish to retain fertility.

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.

Genomic profiling of dedifferentiated endometrial carcinomas arising in the background of high-grade carcinoma: a targeted next-generation sequencing study.

AIMS: Our understanding of dedifferentiated endometrial carcinoma (DEC), a rare and aggressive malignancy, mainly reflects undifferentiated carcinomas (UC) arising in the setting of low-grade endometrial cancer (DEC-LG). However, cases of UC arising in the setting of high-grade EC (DEC-HG) have been noted in the literature. Our knowledge of the genomics of DEC-HG is limited. To characterise the molecular landscape of DEC-HC, targeted genomic sequencing and immunohistochemical analysis was carried out on seven DEC-HG and four DEC-LG. METHODS AND RESULTS: DEC-HG and DEC-LG, including undifferentiated and differentiated components, both showed a similar frequency and spectrum of mutations. ARID1A mutations were identified in 6/7 (86%) DEC-HG and 4/4 (100%) DEC-LG, while SMARCA4 mutations were present in 4/7 (57%) DEC-HG and in 1/4 (25%) DEC-LG. Concurrent SMARCA4/BRG1 protein loss by immunohistochemistry was observed in 3/4 and 1/1 SMARCA4 mutated DEC-HG and DEC-LG, respectively. Neither genomic alterations nor protein loss in SMARCB1/INI1 were observed in any of our cases. TP53 mutations were detected in 4/7 (57%) DEC-HG and in 2/4 (50%) DEC-LG, while mutation-pattern p53 immunohistochemistry expression was observed in 2/7 (29%) DEC-HG and none of the DEC-LG. MLH1 mutations were observed in 1/7 (14%) DEC-HG and 1/4 (25%) DEC-LG. MSH2 and MSH6 mutations were each detected in 1/7 (14%) DEC-HG, but neither was associated with corresponding loss of protein expression. CONCLUSION: The findings support expanding the definition of DEC to include DEC-HG, a previously under-recognised phenomenon with genomic similarities to DEC-LG.