Intratumor heterogeneity of ERBB2 amplification/HER2 overexpression is frequently observed in ERBB2-amplified high-grade endometrial carcinoma (HG-EC) and contributes to anti-HER2 therapy resistance. To elucidate the molecular pathogenesis and evolutionary trajectory of HER2-heterogeneous HG-ECs, we performed next-generation sequencing of spatially distinct HER2-negative (HER2-) and HER2-positive (HER2+) tumor areas from nine tumors (whole exome, n = 7; targeted panel, n = 2). HER2- and HER2+ components shared a high proportion of somatic mutations, particularly clonal mutations, including known EC driver genetic alterations. The 17q12 amplicon, containing the ERBB2 gene, was the only significant recurrent copy number alteration that differed between HER2- and HER2+ components. By unsupervised hierarchical clustering of genome-wide copy number alterations, samples clustered together at the patient level rather than by HER2 status. Intra- and intertumor heterogeneity in ERBB2 amplification/HER2 expression was also observed in metastatic lesions, which likely originated from different tumor subpopulations within the primary tumor. Exploratory spatial transcriptomics analyses revealed gene expression differences associated with HER2 status, including a shift from 'mesenchymal-like' toward epithelial differentiation in HER2+ components for a subset of cases, a finding that warrants further investigation. Our results suggest that HER2 heterogeneity in HG-EC reflects late acquisition of ERBB2 amplification during tumor evolution. ERBB2 does not appear to drive tumor initiation in HER2-heterogeneous HG-EC but likely serves a context-dependent role in the progression of established tumors. © 2026 The Pathological Society of Great Britain and Ireland.

Adult granulosa cell tumors (aGCTs) of the ovary are uniquely characterized by an almost ubiquitous somatic mutation in the FOXL2 gene (p.C134W). We report the first series of 7 aGCTs harboring pathogenic FGFR1 kinase domain mutations, providing a novel alternative oncogenic mechanism in these rare FOXL2 -wildtype tumors. Archival sex cord-stromal tumors that underwent targeted DNA sequencing (MSK-IMPACT, Oncopanel, and Foundation Medicine assays) were reviewed. Histopathologic and immunophenotypic features were reviewed by expert pathologists. Seven cases were identified with FGFR1 hotspot mutations (codons N546, N577, K656, and K687), 6 of which lacked the pathognomonic FOXL2 p.C134W variant. All tumors demonstrated the classic histology of aGCT (microfollicular growth, Call-Exner bodies, "coffee bean" nuclei) with 5/5 showing robust inhibin-α positivity by immunohistochemistry. No distinct morphologic or immunophenotypic differences were found compared with conventional FOXL2 -mutant aGCTs. Clinically, most patients presented at early stage (IA) and underwent surgical management. Four patients experienced recurrent disease involving peritoneal or omental sites, but overall clinical behavior was comparable to typical aGCTs. These findings establish FGFR1 alterations as an alternative oncogenic driver in a subset of FOXL2 -wildtype aGCTs. From a diagnostic standpoint, the absence of FOXL2 p.C134W mutation does not exclude the diagnosis of aGCT when the morphology and immunoprofile are characteristic.

Trastuzumab has demonstrated clinical efficacy in the treatment of HER2-positive serous endometrial cancer (EC), which led to its incorporation into standard-of-care management of this aggressive disease. Acquired resistance remains an important challenge, however, and its underlying mechanisms in EC are unknown. To define the molecular changes that occur in response to anti-HER2 therapy in EC, targeted next-generation sequencing (NGS), HER2 immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) were performed on pre- and post-treatment tumour samples from 14 patients with EC treated with trastuzumab or trastuzumab emtansine. Recurrent tumours after anti-HER2 therapy acquired additional genetic alterations compared with matched pre-treatment ECs and frequently showed decreased HER2 protein expression by IHC (7/14, 50%). Complete/near-complete absence of HER2 protein expression (score 0/1+) observed post-treatment (4/14, 29%) was associated with retained HER2 gene amplification (n = 3) or copy number neutral status (n = 1). Whole-exome sequencing performed on primary and recurrent tumours from the latter case, which exhibited genetic heterogeneity of HER2 amplification in the primary tumour, revealed selection of an early HER2-non-amplified clone following therapy. Our findings demonstrate that loss of target expression, by selection of HER2-non-amplified clones or, more commonly, by downregulation of expression, may constitute a mechanism of resistance to anti-HER2 therapy in HER2-positive EC. © 2023 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Supplementary Figures 1-3 from The High-Mobility Group A1 Gene Up-Regulates Cyclooxygenase 2 Expression in Uterine Tumorigenesis

Obesity, defined as a body mass index (BMI) ≥ 30, is an established risk factor for breast cancer among women in the general population after menopause. Whether elevated BMI is a risk factor for women with a germline mutation in BRCA1 or BRCA2 is less clear because of inconsistent findings from epidemiological studies and a lack of mechanistic studies in this population. Here, we show that DNA damage in normal breast epithelia of women carrying a BRCA mutation is positively correlated with BMI and with biomarkers of metabolic dysfunction. In addition, RNA sequencing showed obesity-associated alterations to the breast adipose microenvironment of BRCA mutation carriers, including activation of estrogen biosynthesis, which affected neighboring breast epithelial cells. In breast tissue explants cultured from women carrying a BRCA mutation, we found that blockade of estrogen biosynthesis or estrogen receptor activity decreased DNA damage. Additional obesity-associated factors, including leptin and insulin, increased DNA damage in human BRCA heterozygous epithelial cells, and inhibiting the signaling of these factors with a leptin-neutralizing antibody or PI3K inhibitor, respectively, decreased DNA damage. Furthermore, we show that increased adiposity was associated with mammary gland DNA damage and increased penetrance of mammary tumors in Brca1 +/− mice. Overall, our results provide mechanistic evidence in support of a link between elevated BMI and breast cancer development in BRCA mutation carriers. This suggests that maintaining a lower body weight or pharmacologically targeting estrogen or metabolic dysfunction may reduce the risk of breast cancer in this population.

Endometrial carcinoma is the most common malignancy of the genital tract in females in the United States, and it is one of the few human cancers increasing in incidence and mortality. Numerous studies have found an association of endometrial carcinoma with obesity, diabetes, and unopposed estrogen stimulation. Molecular studies, in our lab and others, have shown that endometrial carcinoma has a high frequency of alterations in the Phosphoinositide 3-kinase (PIK3) pathway, and notably, coexisting abnormalities in more than one member of the pathway are common. We have combined studies on primary human tumors and genetic mouse models to explore the role of the PIK3 pathway and estrogen, and their interactions, in the development and progression of endometrial carcinoma. Abnormalities in the PIK3 pathway do not simply play redundant roles in endometrial carcinoma and, although not required, the presence of estrogen can alter the course of the disease.

Obesity is an established risk factor for breast cancer among women in the general population after menopause. Whether elevated bodyweight is a risk factor for women with a germline mutation in BRCA1 or BRCA2 is less clear due to inconsistent findings from epidemiological studies and lack of mechanistic studies in this population. Here, we show that DNA damage in normal breast epithelium of BRCA mutation carriers is positively correlated with body mass index and with biomarkers of metabolic dysfunction. Additionally, RNA-sequencing reveals significant obesity-associated alterations to the breast adipose microenvironment of BRCA mutation carriers, including activation of estrogen biosynthesis, which impacts neighboring breast epithelial cells. We found that blockade of estrogen biosynthesis or estrogen receptor activity decreases DNA damage, whereas treatment with leptin or insulin increases DNA damage in BRCA heterozygous epithelial cells. Furthermore, we show that increased adiposity is associated with mammary gland DNA damage and increased penetrance of mammary tumors in Brca1 +/- mice. Overall, our results provide mechanistic evidence in support of a link between bodyweight and breast cancer development in BRCA mutation carriers and suggests that maintaining a healthy bodyweight or pharmacologically targeting estrogen or metabolic dysfunction may reduce the risk of breast cancer in this population. One Sentence Summary Elevated bodyweight is positively associated with DNA damage in breast epithelium of BRCA mutation carriers

Endometrial cancer is the most commonly diagnosed gynecologic malignancy in the United States. Endometrioid endometrial carcinomas constitute approximately 85% of newly diagnosed cases; serous carcinomas represent approximately 3-10% of diagnoses; clear cell carcinoma accounts for <5% of diagnoses; and uterine carcinosarcomas are rare, biphasic tumors. Longstanding molecular observations implicate PTEN inactivation as a major driver of endometrioid carcinomas; TP53 inactivation as a major driver of most serous carcinomas, some high-grade endometrioid carcinomas, and many uterine carcinosarcomas; and inactivation of either gene as drivers of some clear cell carcinomas. In the past decade, targeted gene and exome sequencing have uncovered additional pathogenic aberrations in each histotype. Moreover, an integrated genomic analysis by The Cancer Genome Atlas (TCGA) resulted in the molecular classification of endometrioid and serous carcinomas into four distinct subgroups, POLE (ultramutated), microsatellite instability (hypermutated), copy number low (endometrioid), and copy number high (serous-like). In this review, we provide an overview of the major molecular features of the aforementioned histopathological subtypes and TCGA subgroups and discuss potential prognostic and therapeutic implications for endometrial carcinoma.

Historically, endometrial carcinomas have been classified primarily according to their histology. However, the use of immunohistochemistry has become commonplace in their evaluation, particularly in diagnostically challenging cases. Our objective was to evaluate mixed endometrial carcinomas using a well-established panel of biomarkers to assess the consistency and utility of these stains in clinical diagnosis. Eighteen cases comprised of various combinations of classical serous (SC), endometrioid (EC), and clear cell (CC) morphologies were identified and subjected to a panel of immunohistochemical markers including p53, p16, Ki67, estrogen receptor, progesterone receptor, and Napsin A. Intensity and extent of staining were evaluated on 4-tiered and 5-tiered scales, respectively. The typical immunostaining pattern expected for the individual tumor components was seen in only 3 cases, while in 15 cases an unexpected pattern was observed with at least one immunomarker. By tumor type, the most common unexpected finding in EC/SC carcinoma cases was diffuse positivity for p16 and/or estrogen receptor/progesterone receptor in both components, while in SC/CC, diffuse positivity for p53 in both components was most frequently seen, and in SC/CC/EC, Napsin A negativity was most commonly observed. Despite displaying diagnostic morphology, components of many mixed endometrial carcinomas may not exhibit expected immunohistochemical features. This may be due to the fact that these carcinomas arise from a single clone with subsequent divergence, resulting in a tumor with both mixed histologic and genetic features. It is important to note that these tumors may not demonstrate the immunohistochemical prototype of their constituents and should be approached accordingly from a diagnostic perspective.

The aim of this article is to propose guidelines and recommendations in problematic areas in pathologic reporting of endometrial carcinoma (EC) regarding special techniques and ancillary studies. An organizing committee designed a comprehensive survey with different questions related to pathologic features, diagnosis, and prognosis of EC that was sent to all members of the International Society of Gynecological Pathologists. The special techniques/ancillary studies group received 4 different questions to be addressed. Five members of the group reviewed the literature and came up with recommendations and an accompanying text which were discussed and agreed upon by all members of the group. Twelve different recommendations are made. They address the value of immunohistochemistry, ploidy, and molecular analysis for assessing prognosis in EC, the value of steroid hormone receptor analysis to predict response to hormone therapy, and parameters regarding applying immunohistochemistry and molecular tests for assessing mismatch deficiency in EC.

The discovery of displaced granulosa cells in the fallopian tube is concerning for a granulosa cell neoplasm and can lead to further surgical intervention. Discerning the risk of neoplasm can be challenging, even with immunohistochemical staining of CD56, a highly sensitive marker of granulosa cell neoplasm. A 48-year-old underwent an uncomplicated hysterectomy and bilateral salpingectomy for symptomatic fibroids and was found to have a small focus of granulosa cells staining positive for CD56 in her left fallopian tube. Post-operative imaging demonstrated a left adnexal mass. The patient underwent a left oophorectomy. Final pathology demonstrated a benign mucinous cystadenofibroma without evidence of granulosa cell neoplasm. Displaced granulosa cells require further pathologic and surgical evaluation, but do not always equate to neoplasm and should be managed accordingly.

Ovarian cancers diagnosed between 2000 and 2013 were examined and cases with and without endometriosis compared. Among 139 epithelial ovarian, there were 49 (35%) with endometriosis and 90 (65%) without endometriosis. Endometriosis associated ovarian cancers were more likely to be confined to the pelvis (54% vs. 9%, p < 0.0001) and lower grade (51% vs. 29%, p = 0.014). Younger age and earlier stage independently predicted the presence of endometriosis (p = 0.0011 and p < 0.0001, respectively). Ovarian cancer patients with endometriosis had improved PFS and OS [(HR = 0.20; 95% CI, 0.09-0.43), (HR = 0.18; 95% CI, 0.04-0.81)], compared to patients without endometriosis; however, endometriosis had no independent prognostic significance.

We are fortunate to work in a discipline with a rich tradition. Indeed, few subspecialty areas in pathology have more fascinating stories than those associated with personalities and entities in gynecologic pathology. Many of these have been the subject of essays in the Journal’s history series that have focused on many of the luminaries in our field, dating back to 1996 with the first such contribution, devoted to Dr Thomas S. Cullen, the pioneer of gynecologic pathology at Johns Hopkins Hospital and, arguably, in North America. Another feature with a historical flavor that we hope readers have enjoyed are the occasional interviews with distinguished figures in our field. Those that have already appeared featured two of the Society’s past presidents, Dr Robert E. Scully and Dr Harold Fox. Further contributions of this nature are encouraged but prior approval of the Editor-in-Chief should be obtained, it being our intention that these interviews be restricted to individuals of the highest stature. We wish here to draw attention to a new vehicle for two types of contributions that will focus on diagnoses having interesting historical aspects. One category would pertain to articles focusing on one of the many diagnostic eponyms in gynecologic pathology, these bringing a human aspect to a lesion and in many instances an associated intriguing story behind the birth of the eponym. A wonderful book on eponyms in obstetrical and gynecologic pathology is noted in the inaugural essay in this issue. The second category would be noneponymous processes that are associated with an interesting history behind their birth. Our discipline certainly has no shortage of remarkable neoplastic and non-neoplastic processes and tales associated with their discovery. One of the most fascinating stories is the recognition by Dr Javier Arias-Stella of the microscopic finding that is now designated by one of the best known eponyms in gynecologic pathology. We are delighted that the senior author of this essay is Dr Juan Rosai, someone whose own immense contributions to the field of pathology need no comment. Some readers will have had the good fortune over the years to hear Dr Rosai’s remarkable lecture on entities in surgical pathology. It is appropriate that the story of Dr Arias-Stella and his reaction, although written about to some extent in other sources, is presented for the society membership in the pages of our Journal. We invite essays of a similar nature, subject to customary peer review. Should anyone wish to contribute an essay focusing on a famous eponym or a noneponymous neoplasm or tumor-like lesion, they should feel free to contact us. As the pages in the Journal must be largely devoted to original peer-reviewed contributions, essays of the type encouraged can only be an occasional feature and modest in length. It is our hope that these contributions will provide the reader an enjoyable break from the standard contributions, broaden our knowledge of the pathology of an entity, and add to our ongoing recognition of those who have contributed to our field.

Objectives: Mutations in FBXW7, a tumor suppressor gene that regulates ubiquitination, are associated with chemotherapy resistance in solid cancers. Inactivation of FBXW7 leads to over-expression of pro-survival proteins (McL-1, Notch1, and CyclinE1). Upto 9–17% of type 2 endometrial cancers harbor these mutations. Our objective was to demonstrate chemotherapy-resistance in FBXW7-mutated endometrial cancer cell lines.

ObjectivesType II endometrial carcinomas—uterine carcinosarcomas or uterine malignant mesodermal mixed tumors (UMMMTs), clear cell carcinomas (UCCs), and uterine serous carcinomas (USCs)—are aggressive malignancies that present with advanced disease and have high mortality rates. PIK3CA mutations are commonly found in endometrial cancers. The objective of the study was to characterize molecular alterations in the PIK3CA gene in these tumors. MethodsA total of 84 cases (20 UMMMTs, 18 UCCs, and 46 USCs) were selected from the surgical pathology files of Weill Cornell Medical College and Johns Hopkins Hospital. The diagnoses were confirmed by gynecologic pathologists (L.H.E. and A.Y.). DNA was extracted from paraffin-embedded tissue. Polymerase chain reaction was performed for mutational analysis. All the studies were performed in accordance with approved Institutional Review Board protocols. ResultsMutations in the PIK3CA gene were identified in 3 (15%) of 20 UMMMT, 3 (16.7%) of 18 UCC, and 10 (21.7%) of 46 USC cases. We report novel mutations in PIK3CA in uterine carcinosarcoma. ConclusionsA significant percentage of UMMMTs, UCCs, and USCs have mutations in PIK3CA. Further investigation is needed to develop targeted therapies for these aggressive uterine cancers.