Endometrioid Carcinomas of the Uterine Corpus With Sex Cord-like Formations, Hyalinization, and Other Unusual Morphologic Features

Endometrial Carcinosarcomas are Almost Exclusively of p53abn Molecular Subtype After Exclusion of Mimics

SUMMARY

Our aim was to assess the molecular subtype(s) and perform a detailed morphologic review of tumors diagnosed as carcinosarcoma in a population-based cohort. Forty-one carcinosarcomas were identified from a cohort of 973 endometrial carcinomas diagnosed in 2016. We assessed immunostaining and sequencing data and undertook expert pathology reviews of these cases as well as all subsequently diagnosed (post-2016) carcinosarcomas of no specific molecular profile (NSMP) molecular subtype (n=3) from our institutions. In the 2016 cohort, 37 of the 41 carcinosarcomas (91.2%) were p53abn, 2 (4.9%) were NSMP, and 1 each (2.4%) were POLE mut and mismatch repair deficiency molecular subtypes, respectively. Of the 4 non-p53abn tumors on review, both NSMP tumors were corded and hyalinized (CHEC) pattern endometrioid carcinoma, the mismatch repair deficiency tumor was a grade 1 endometrioid carcinoma with reactive stromal proliferation, and the POLE mut tumor was grade 3 endometrioid carcinoma with spindle cell growth, that is, none were confirmed to be carcinosarcoma on review. We found 11 additional cases among the 37 p53abn tumors that were not confirmed to be carcinosarcoma on the review (3 undifferentiated or dedifferentiated carcinomas, 5 carcinomas with CHEC features, 2 carcinomas showing prominent reactive spindle cell stroma, and 1 adenosarcoma). In the review of institutional cases reported as NSMP carcinosarcoma after 2016, 3 were identified (1 adenosarcoma and 2 mesonephric-like adenocarcinoma on review). In this series, all confirmed endometrial carcinosarcomas were p53abn. The finding of any other molecular subtype in a carcinosarcoma warrants pathology review to exclude mimics.

Endometrial serous carcinoma with a corded and hyalinized pattern: a clinicopathological and molecular analysis

A corded and hyalinized pattern has been described in endometrial endometrioid carcinoma. Herein, we describe a clinicopathological and molecular analysis of the first reported case of endometrial serous carcinoma with a corded and hyalinized pattern.

A 64-year-old woman underwent hysterectomy and bilateral salpingo-oophorectomy due to a 5.5 cm endometrial lesion. Histologically, the tumor was composed of a minor (20%) serous carcinoma component and a predominant corded component embedded in a hyaline-to-myxoid matrix. This component showed diffuse and strong p53 and p16 expression, heterogeneous positivity for epithelial markers and WT1, focal positivity for estrogen and progesterone receptors, retained MMR, SMARCA4/BRG1, and SMARCB1/INI1 expression, and negativity for smooth muscle, germ cell, sex cord, neuroendocrine, endothelial, and melanocytic markers and GATA3. Next-generation sequencing showed a mutation of uncertain significance in APC and no mutations in MLH1, MSH2, MSH6, PMS2, MUTYH, POLE, POLD1, EPCAM, or CTNNB1. The patient had a recurrence on the vaginal stump after 15 months.

In conclusion, endometrial serous carcinoma can show a corded and hyalinized pattern, which may represent a diagnostic challenge.

Corded and Hyalinized Endometrioid Endometrial Carcinoma: A Rare Case Treated With Robot-Assisted Surgery

Endometrial carcinoma is the sixth most common cancer among women worldwide. Minimally invasive surgery (MIS) has become the preferred treatment, offering similar survival outcomes to laparotomy with lower complication rates. Corded and hyalinized endometrioid carcinoma (CHEC) is a rare and diagnostically challenging variant of endometrioid carcinoma, first described in 2005, characterized by a biphasic appearance of traditional low-grade endometrioid adenocarcinoma and corded and spindled cells embedded in a hyaline stroma. A 55-year-old nulligravid woman presented with abnormal genital bleeding for 10 days. Initial evaluations, including transvaginal ultrasonography and histological examination, confirmed adenocarcinoma. Imaging studies (magnetic resonance imaging [MRI] and computed tomography [CT]) revealed a thickened endometrium (11 mm) with no myometrial invasion, enlarged pelvic lymph nodes, or distant metastasis. Tumor markers were within normal ranges. She underwent robot-assisted laparoscopic total hysterectomy, bilateral adnexectomy, and pelvic lymph node biopsy using the da Vinci Xi system (Intuitive Surgical, Sunnyvale, CA). Histopathological examination revealed CHEC, with characteristic epithelioid and spindled cells arranged in cords within a hyalinized stroma. Immunohistochemical staining showed focal positivity for cytokeratin AE1/AE3, weak estrogen receptor positivity, and nuclear β-catenin expression, distinguishing it from carcinosarcoma. The diagnosis was confirmed as CHEC, FIGO 2008 stage IA (pT1aN0M0). The patient remained disease-free 18 months post-surgery. CHEC is a rare variant of endometrioid carcinoma with unique histological features. It typically presents in younger patients at an early stage and has a favorable prognosis. Accurate diagnosis is crucial to differentiate it from more aggressive tumors like carcinosarcoma, preventing overtreatment. The immunohistochemical profile, particularly nuclear β-catenin accumulation, is useful in distinguishing CHEC from carcinosarcoma. This is the first documented case of CHEC successfully treated with robot-assisted surgery. Increased awareness among pathologists and clinicians is essential for accurate diagnosis and optimal management of this rare tumor variant.

Special Considerations in Classification and Workup of Endometrial Carcinomas

CONTEXT.—

A variety of uncommon malignant endometrial tumors can be challenging to diagnose because of overlapping morphology with more common entities. In some cases, immunohistochemical stains and/or molecular testing allow for more definitive diagnosis or prognostication.

OBJECTIVE.—

To review classic morphologic features of uncommon endometrial tumors, pathologic features of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in the diagnosis of these tumors.

DATA SOURCES.—

University of Michigan (Ann Arbor) cases and review of pertinent literature about each entity.

CONCLUSIONS.—

Although each of these uncommon endometrial tumors has morphologic mimics, key histologic features, immunohistochemical stains, and molecular testing allow for accurate classification.

Uterine Tumors Resembling Ovarian Sex Cord Tumors (UTROSCTs): A Scoping Review of 511 Cases, Including 2 New Cases

Uterine Tumors Resembling Ovarian Sex Cord Tumors (UTROSCTs) are rare uterine mesenchymal neoplasms with uncertain biological potential. These tumors, which affect both premenopausal and postmenopausal women, usually have a benign clinical course. Nevertheless, local recurrences and distant metastases have been described. By analyzing 511 cases retrieved from individual reports and cases series, we provide here the most comprehensive overview of UTROSCT cases available in the literature, supplemented by two new cases of UTROSCTs. Case 1 was an asymptomatic 31-year-old woman who underwent a laparoscopic resection of a presumed leiomyoma. Case 2 was a 58-year-old postmenopausal woman with abnormal vaginal bleeding who underwent an outpatient hysteroscopic biopsy of a suspicious endometrial area. In both cases, immunohistochemical positivity for Calretinin and Inhibin was noted, typical for a sex cord differentiation. In both cases, total laparoscopic hysterectomy with bilateral salpingo-oophorectomy was performed. In light of the available literature, no pathognomonic clinical or imaging finding can be attributed to UTROSCT. Patients usually present with abnormal uterine bleeding or pelvic discomfort, but 20% of them are asymptomatic. In most cases, a simple hysterectomy appears to be the appropriate treatment, but for women who wish to become pregnant, uterus-preserving approaches should be discussed after excluding risk factors. Age, tumor size, lymphovascular space invasion, nuclear atypia, and cervical involvement are not reliable prognostic factors in UTROSCT. The current research suggests that aggressive cases (with extrauterine spread or recurrence) can be identified based on a distinct genetic and immunohistochemical phenotype. For instance, UTROSCTs characterized by GREB1::NCOA1-3 fusions and PD-L1 molecule expression appear to be predisposed to more aggressive behaviors and recurrence, with GREB1::NCOA2 being the most common gene fusion in recurrent tumors. Hence, redefining the criteria for UTROSCTs may allow a better selection of women suitable for fertility-sparing treatments or requiring more aggressive treatments in the future.

Endometrioid carcinomas with sex cord-like formations and hyalinization: spontaneous pregnancy after conservative treatment

Endometrioid carcinoma with sex cord-like formations and hyalinization of the uterine corpus, or corded and hyalinized endometrioid adenocarcinoma (CHEC), is a rare morphological variant of endometrioid carcinoma, for which there is limited literature and few cases reports. Most researchers tend to consider CHEC as a low-grade cancer with a favorable prognosis. Full-staging surgery is the primary choice for this disease, and no case of CHEC has been previously reported to be treated conservatively. Here, we present the following case to explore the possibility of fertility-preserving treatment for young women with CHEC. A 23-year-old nulliparous patient diagnosed with presumed stage IA CHEC received fertility-sparing treatment at the Obstetrics and Gynecology Hospital of Fudan University and got a complete response (CR) after 10 months of conservative treatment. The patient subsequently became pregnant spontaneously, successfully conceived, and gave birth to a healthy male neonate without any sign of recurrence during 37 months follow-up after CR. The patient's postpartum follow-up is continuing. Presently, CHEC is not included in the fertility-sparing field of any available guidelines. This case indicates that fertility-sparing treatment may be an option for highly selected patients with CHEC. Continuous follow-up remains mandatory to observe long-term outcomes.

Practical Updates and Diagnostic Challenges in Endometrial Carcinoma

CONTEXT.—

Clinical management of endometrial carcinoma largely depends on the morphologic parameters ascertained based on the pathologic evaluation of surgical resection specimens. However, there are numerous controversial and nonstandardized aspects of both the macroscopic and microscopic assessment of surgical specimens, including grossing, adequate sampling, diagnosis, staging, reporting, and ancillary testing.

OBJECTIVE.—

To provide a comprehensive practical review of standardized grossing, key morphologic findings for reporting and staging, and diagnostic and prognostic use of ancillary testing in endometrial carcinomas.

DATA SOURCES.—

The existing literature, recommendations of the International Society of Gynecological Pathologists, and specialty consensus guidelines.

CONCLUSIONS.—

This review article summarizes important aspects of the grossing and sampling of surgical resection specimens for microscopic examination, key morphologic parameters that are required for reporting and staging, and morphologic features and immunoprofiles helpful in the differential diagnosis of low-grade and high-grade endometrial carcinomas, as well as the current status of the molecular classification of endometrial carcinoma and human epidermal growth factor receptor 2 testing in serous carcinoma. The information presented herein can be helpful in overcoming diagnostic challenges and issues related to the pathology reporting of endometrial carcinoma to practicing anatomic pathologists.

Relevance of Molecular Pathology for the Diagnosis of Sex Cord-Stromal Tumors of the Ovary: A Narrative Review

Ovarian sex cord-stromal tumors (SCSTs) account for 8% of all primary ovarian neo-plasms. Accurate diagnosis is crucial since each subtype has a specific prognostic and treatment. Apart from fibrosarcomas, stromal tumors are benign while sex cord tumors may recur, sometimes with a significant time to relapse. Although the diagnosis based on morphology is straightforward, in some cases the distinction between stromal tumors and sex cord tumors may be tricky. Indeed, the immunophenotype is usually nonspecific between stromal tumors and sex cord tumors. Therefore, molecular pathology plays an important role in the diagnosis of such entities, with pathognomonic or recurrent alterations, such as FOXL2 variants in adult granulosa cell tumors. In addition, these neoplasms may be associated with genetic syndromes, such as Peutz-Jeghers syndrome for sex cord tumors with annular tubules, and DICER1 syndrome for Sertoli-Leydig cell tumors (SLCTs), for which the pathologist may be in the front line of syndromic suspicion. Molecular pathology of SCST is also relevant for patient prognosis and management. For instance, the DICER1 variant is associated with moderately to poorly differentiated SLCTS and a poorer prognosis. The present review summarizes the histomolecular criteria useful for the diagnosis of SCST, using recent molecular data from the literature.

Treatment With Antitumor Agents Recommended by Cancer Genome Panel for Uterine Leiomyosarcoma

To date, cancer genomic medicine, using cancer gene panel covered by health insurance from June 2019, has been performed for advanced malignant tumors under public medical insurance. In gynecology, the first-line treatment for uterine leiomyosarcomas, which is a mesenchymal uterine tumor, is surgery. In uterine leiomyosarcoma cases, recurrence is observed within 2 years postoperatively; however, to date, clinical trials have not shown efficacy with existing antitumor agents. We noted efficacy in two cases with advanced/recurrent uterine leiomyosarcoma using an antitumor agent selected on the basis of cancer gene panel testing results. Following uterine leiomyosarcoma diagnosis, they underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy as standard surgical treatment. After the surgical treatment, the imaging test revealed recurrent tumors; subsequently, they were treated with doxorubicin alone or doxorubicin combined with Gemzar. However, cancer genome gene panel test was performed because the malignant tumor worsened. Based on the cancer genome gene panel test results, the two cases with advanced uterine leiomyosarcoma were associated with increased tumor mutational burden (TMB) or pathogenic variants (PVs) of AKT serine/threonine kinase 1 (AKT1). Therefore, treatment with pembrolizumab, which is a drug covered by insurance for patients with TMB-high, or treatment with kinase inhibitors for patients with PVs in AKT, was considered. Cancer genomic medicine using cancer gene panel provides a new treatment strategy for intractable malignant tumors. This study aimed to discuss the usefulness of cancer genomic medicine by cancer gene panel testing using the cases of advanced and recurrence uterine leiomyosarcoma and the latest findings.

High-grade serous ovarian carcinoma with a sertoliform pattern associated with BRCA mutation: a clinicopathological and molecular analysis

Herein, we report a clinicopathological and molecular analysis of a case of tubo-ovarian high-grade serous carcinoma (HGSC) with a sertoliform pattern. A 45-year-old woman underwent surgery due to an advanced bilateral adnexal carcinoma with peritoneal and appendiceal metastases. Histological examination revealed an HGSC exhibiting a distinct sertoliform component. Such component showed diffuse PAX8, p53 (mutation-type), and p16 (block-type) expression, increased vimentin and decreased WT1 expression compared to the conventional HGSC component, membrane β-catenin positivity, heterogeneous estrogen, and progesterone positivity, and retained PTEN and mismatch repair expression and negativity for GATA3, TTF1, inhibin, calretinin, CD10, CDX2, chromogranin, and synaptophysin. Molecular analysis showed a germline BRCA2 mutation; no mutations were detected in POLE, POLD1, MLH1, MSH2, MSH6, PMS2, APC, CTNNB1, MUTYH, and EPCAM. In conclusion, a sertoliform pattern can be part of the morphological spectrum of BRCA-related HGSC.

The Evolving Spectrum of Endometrial Glandular Proliferations With Corded and Hyalinized Features

We present the clinicopathologic and immunohistochemical features of 14 endometrial glandular proliferations with conspicuous corded and hyalinized (CH) features comprised entirely or predominantly of endometrial hyperplasia. Endometrial glandular lesions ranged in severity from endometrial hyperplasia with and without cytologic atypia (5/14 [36%]) to hyperplasia with architectural complexity bordering on well-differentiated endometrioid adenocarcinoma (3/14 [21%]) to frank corded and hyalinized endometrial carcinoma ("CHEC") (6/14 [43%]). In addition to sex cord-like growth and hyalinized stroma, other common histologic features included prominent spindle cells (11/14 [79%]), keratinizing and/or morular squamous differentiation (10/14 [71%]), and osseous metaplasia (6/14 [43%]). Immunohistochemical characterization revealed aberrant nuclear beta-catenin in all cases (14/14 [100%]); additionally, all cases demonstrated positive estrogen receptors, intact PTEN, PMS2 and MSH6, and wild-type p53 expression. Patients ranged in age from 24 to 58 (mean 38) years. Of 5 patients with hyperplasia with CH features, 2 experienced complete resolution after progestin therapy and none progressed to adenocarcinoma (mean follow-up 15.6 mo, range 2 to 64). By contrast, of 2 patients with hyperplasia bordering on CHEC and with available follow-up, both subsequently developed adenocarcinoma, suggesting that even focal increased architectural complexity may predict an elevated risk of malignancy. We conclude that CH morphology is not limited to endometrioid carcinoma and may occur across a spectrum of neoplastic proliferations, including those without sufficient architectural complexity or cytologic atypia to warrant classification as adenocarcinoma. We propose the term "corded and hyalinized endometrial hyperplasia" to describe this precursor lesion and report favorable outcomes with conservative treatment.

Sclerosis in Sex Cord-Stromal Tumors Other Than the Sclerosing Stromal Tumor: A Report of 70 Cases

Sclerosis is well-known in sclerosing stromal tumors (SSTs), as its name indicates, but has not been evaluated in other ovarian sex cord-stromal tumors (SCSTs). Its presence in other SCSTs has sporadically caused diagnostic problems in cases we have seen, and this prompted us to review SCSTs with appreciable sclerosis; tumors containing at least 20% sclerosis were included. Seventy cases were identified: 20 thecomas, 20 juvenile granulosa cell tumors (JGCTs), 8 adult granulosa cell tumors (AGCTs), 5 sex cord tumors with annular tubules, 6 retiform Sertoli-Leydig cell tumors (SLCTs; all of the intermediate differentiation), 4 nonretiform SLCTs (3 well-differentiated, 1 of intermediate differentiation with heterologous elements), 4 Sertoli cell tumors, and 3 microcystic stromal tumors (MSTs). Paucicellular sclerotic zones comprised 20% to 95% of the tumors and when conspicuous often obscured diagnostic features. Thirty-one tumors (10 thecomas, 19 JGCTs, 1 AGCT, and 1 MST) showed sclerotic zones focally enveloping nodules of tumor cells, imparting a pseudolobular appearance, and sclerosis often occurred within lobules as well. Ten of these (5 thecomas and 5 JGCTs) also had prominent staghorn blood vessels, generating a low-power appearance focally similar to SST. In 17 tumors, the sclerosis resulted in "compression" of the tumor cells into cords and/or solid tubules. Correct diagnosis in these cases is dependent on careful examination of the cellular zones of the neoplasms, but awareness of the extent of sclerosis that may be seen in diverse SCSTs may be crucial in suggesting the correct diagnosis particularly when the material is limited as in the intraoperative setting. Our findings highlight for the first time the occurrence and character of sclerosis in sex cord tumors other than SSTs and fibromas. Sclerosis is seen in descending proportion of the tumor types as follows: retiform SLCTs, thecomas, MSTs, JGCTs, sex cord tumors with annular tubules, Sertoli cell tumors, AGCTs, and nonretiform SLCTs. Its character can vary somewhat, having particular features in the sex cord tumor with annular tubules (hyaline material within tubules often coalescing and extending beyond the nests to form confluent aggregates) and retiform SLCTs (common in papillary cores).

Corded and hyalinized endometrioid carcinoma: Summary of clinical, histological, immunohistochemical and molecular data

Corded and hyalinized endometrioid carcinoma (CHEC) represents a potential pitfall for pathologists. This study aimed to provide a complete overview of all clinicopathological and molecular features of CHEC. Electronic databases were searched for all published series of CHEC. Clinical, histological, immunohistochemical and molecular data about CHEC were extracted and pooled. Six studies with 62 patients were identified; mean age was 49.8 years (range 19-83). Most cases showed FIGO stage I (68%), low grade (87.5%), and a favorable outcome (78.4%), with "no specific molecular profile" (NSMP). A subset of cases showed high-grade features (12.5%), p53 abnormalities (11.1%) or mismatch repair (MMR) deficiency (20%) and occurred at an older age (mean age>60 years). Common features of CHEC were: superficial localization of the corded component (88.6%), squamous/morular differentiation (82.5%), nuclear β-catenin accumulation (92%), partial/total loss of CKAE1/AE3 (88.9%), estrogen receptor (95.7%) and e-cadherin (100%), stromal changes such as myxoid (38.5%), osteoid (24%) and chondroid (4.5%), CTNNB1 mutations (57.9%), and POLE-wild-type (100%); 24.4% of cases showed lymphovascular space invasion. A minority of cases (16.2%) showed poor outcome despite a low-grade, NSMP phenotype; the molecular basis for the aggressiveness of these cases is still undefined. Further studies are necessary in this field.

The diverse morphology and immunophenotype of ovarian endometrioid carcinomas

Endometrioid carcinoma (EC) accounts for approximately 10-12% of ovarian epithelial malignancies but compared to its relative frequency, results in a disproportionate number of diagnostically difficult cases with potential for misdiagnosis. In this review the protean and diverse morphologies of ovarian EC are discussed, including 'metaplastic' changes, EC with spindle cell differentiation/corded and hyalinised features and EC with sex cord-like formations. The propensity for 'transdifferentiation' in ovarian ECs is also discussed, one example being the association with a somatically derived yolk sac tumour. Although immunohistochemistry may be extremely useful in diagnosing EC and in distinguishing between EC and other ovarian epithelial malignancies, metastatic neoplasms and sex cord-stromal tumours, this review also discusses the propensity for ovarian EC to exhibit an aberrant immunophenotype which may compound diagnostic uncertainty. The genomic characteristics of these tumours and the recent 'incorporation' of seromucinous carcinoma into the EC category are also discussed.

Uterine Tumors Resembling Ovarian Sex Cord Tumors: A Clinicopathologic Study of 75 Cases Emphasizing Features Predicting Adverse Outcome and Differential Diagnosis

Uterine tumors resembling ovarian sex cord tumors (UTROSCTs), first characterized by Drs Clement and Scully in 1976, are rare neoplasms showing clinical, morphologic, and immunohistochemical overlap with a number of other uterine tumors, most being mesenchymal. Criteria for aggressive behavior are not clearly established. We report 75 tumors from patients ranging from 21 to 84 (mean=52.4) years. Seventy-one patients were treated by hysterectomy and 4 by conservative total excision. Thirty-eight tumors were intramyometrial, 34 submucosal, and 3 cervical; they ranged from 0.6 to 20 (mean=4.9) cm and were typically tan-yellow. Sixty-eight neoplasms were well-circumscribed and 7 had infiltrative borders (4 only minimally). In 56 tumors, a smooth muscle component was intimately admixed with the neoplastic cells ("pseudoinfiltration"; extensive in 29). Architectural patterns included cords (n=53), diffuse (n=51), hollow tubules (n=48), nests (n=38), trabeculae (n=37), retiform (n=23), solid tubules (n=21), pseudoangiomatoid (n=11), pseudopapillary (n=4), and whorled (n=2); typically, more than 1 pattern was seen. Tumor cells were epithelioid (n=62), epithelioid and spindled (n=12), or spindled (n=1) and/or rhabdoid (n=20; extensive in 2). Cytologic atypia was absent to mild in 57, moderate in 16, and moderate to severe in 2 tumors. Fifty-seven UTROSCTs had ≤2mitoses/10 high power fields (HPF), 12 had 3 to 5/10 HPF, and 6 >5/10 HPF. Necrosis was present in 3 and lymphovascular invasion in 1. Tumor cells showed a polyphenotypic immunohistochemical profile (with positivity for sex cord, smooth muscle, and epithelial markers), most commonly inhibin (17/33+) and calretinin (22/31+) positive. Five of 58 patients with follow-up (22 to 192; mean=73.2 mo) had recurrences/metastases from 30 to 144 months, and 2 died of disease. Malignant tumors showed >3 of the following 5 features compared with benign tumors: size >5 cm, at least moderate cytologic atypia, ≥3 mitoses/10 HPF, infiltrative borders, and necrosis. One of the 5 malignant tumors showed an extensive rhabdoid morphology. UTROSCTs are uncommon, show a wide morphologic spectrum, often pose problems in differential diagnosis, and typically have a benign outcome. Rare tumors are associated with late recurrences and a combination of more than 3 of the 5 features listed above predicted aggressive behavior in this series.

Microscopic Sertoliform Sex Cord Proliferations: A Rare Incidental Finding Associated With Endometriosis and Ovarian Epithelial Neoplasia

Microscopic sex cord proliferations are a rare incidental finding seen in association with ovarian and uterine stromal or epithelial neoplasms and more uncommonly non-neoplastic conditions such as endometriosis and adenomyosis. They may also occur in the absence of other pathology, as an incidental finding in the ovaries of pregnant women and in heterotopic locations such as the fallopian tube. Most reports of this phenomenon describe adult granulosa cell tumor-like morphology. Herein, we describe 4 cases of microscopic sex cord proliferations with Sertoliform features, occurring in the stromal component of endometriosis or in the wall of an epithelial ovarian neoplasm; 2 of the patients with endometriosis had concurrent endometrioid adenocarcinoma (1 uterine corpus, 1 ovary). The proliferations were positive with sex cord markers inhibin and calretinin. As far as we are aware, such Sertoliform proliferations have not been reported previously in endometriosis and have only rarely been described in association with ovarian epithelial neoplasia. It is likely that such proliferations represent a benign non-neoplastic phenomenon. Awareness of this phenomenon is important in order to avoid misdiagnosis as a sex cord or other neoplasm. In reporting this unusual phenomenon, we review incidental sex cord and sex cord-like proliferations in the female genital tract.

Corded and hyalinized endometrioid endometrial carcinoma with high-grade features: a clinicopathological and TCGA-based molecular analysis

Corded and hyalinized endometrioid carcinoma (CHEC) typically shows low-grade features and "no specific molecular profile" (NSMP). This study aimed to perform a clinicopathological and molecular characterization of endometrial CHEC with high-grade features. Immunohistochemistry for cytokeratin AE1/AE3, e-cadherin, β-catenin, estrogen receptor, progesterone receptor, p53, p16, and mismatch repair proteins was performed. A next-generation sequencing kit was used to assess POLE, POLD1, APC, MLH1, MSH2, MSH6, PMS2, MUTYH, EPCAM, and CTNNB1. Molecular groups, i.e., POLE-mutant, mismatch repair deficient (MMRd), p53-abnormal, and NSMP, were assigned according to the TCGA classifier. Six high-grade endometrial CHECs were identified. The mean age was 57.5 years; 5/6 cases were uterine-confined. Five cases showed a diffusely and markedly atypical corded component and a MMRd or p53-abnormal signature; additional features included single-cell keratinization, necrosis, osteoid or myxoid/chondro-myxoid matrix, foci of anaplasia, and nuclear β-catenin expression. The remaining case showed a low mitotic count and a NSMP phenotype, with focal bizarre cells in an otherwise classical CH endometrioid carcinoma. All cases showed variably reduced expression of epithelial markers and hormone receptors in the corded component. No mutations were found in any of the analyzed genes. In conclusion, high-grade CHECs are a heterogeneous subset of biphasic endometrial carcinoma which show similarities and differences with classical CHEC and carcinosarcoma. These cases often show MMRd or p53-abnormal signatures.

ZEB1 expression is frequently detected in undifferentiated and dedifferentiated carcinomas, but is not specific among endometrial carcinomas

AIMS

The pathological diagnosis of undifferentiated and dedifferentiated endometrial carcinomas (UC/DCs) is prognostically important. However, undifferentiated components may be confused with other subtypes, particularly grade 3 endometrioid carcinomas (G3ECs). ZEB1 has recently been identified as a promising marker because it is frequently expressed in the undifferentiated components of UC/DCs, but not in other carcinomas. Therefore, we herein evaluated the diagnostic utility of ZEB1 with an emphasis on distinguishing between UC/DCs and G3ECs using an expanded cohort of endometrial carcinomas and carcinosarcomas.

METHODS AND RESULTS

Immunostaining for ZEB1 was performed on whole-tissue sections of 19 UC/DCs, 194 non-UC/DC endometrial carcinomas, and 29 carcinosarcomas. Staining was defined as negative (<5%), focal (5-50%), and diffuse expression (>50%). ZEB1 was expressed in 84% of the undifferentiated components of UC/DCs (diffuse in 14, focal in two). Focal expression was observed in eight non-UC/DC endometrial carcinomas and diffuse expression in seven, with the latter comprising G3ECs (4/76), serous carcinoma (1/37), clear cell carcinoma (1/21), and neuroendocrine carcinoma (1/3). Epithelial differentiation was morphologically and immunohistochemically less evident in G3ECs and neuroendocrine carcinoma with diffuse ZEB1 expression. All carcinosarcomas showed diffuse ZEB1 expression in their sarcomatous components.

CONCLUSION

Immunostaining for ZEB1 was sufficiently sensitive to detect undifferentiated components. Diffuse ZEB1 expression showed high specificity for distinguishing between undifferentiated components and G3ECs; however, ZEB1 expression was not entirely specific to UC/DCs. The integration of ZEB1 into the diagnosis of UC/DCs requires careful examinations to exclude other tumours, such as less differentiated G3ECs, neuroendocrine carcinomas, and carcinosarcomas.

A Case of Endometrial Carcinosarcoma Containing Sertoliform Endometrioid Carcinoma Component

Carcinosarcomas (CSs) of the endometrium have admixture of malignant epithelial and mesenchymal components. The carcinomatous component exhibit endometrioid, serous, or clear cell differentiation, or are undifferentiated. CSs are considered homologous or heterologous according to the type of sarcomatous component. Sertoliform endometrioid carcinomas (SECs) of the endometrium which comprise a rare subtype of endometrial cancer, typically occur in the ovary. SECs as a carcinomatous component of CS of the endometrium have not been reported. Here, we report an endometrial carcinosarcoma that contains an SEC component. An 88-year-old female presented to a clinic with atypical genital bleeding. She was referred to our hospital and underwent total hysterectomy, bilateral adnexectomy and partial omentectomy due to endometrial carcinoma. Gross examination revealed a polypoid mass in the uterine cavity with massive myometrial invasion. Histologically, the tumor was a high-grade endometrioid carcinoma. In addition to an ordinary conventional endometrioid carcinoma, approximately 30% of the area exhibited sex cord-like pattern and contained small hollow tubules, anastomosing cords and trabeculae, and tightly packed nests. Immunohistochemically, the SEC component showed diffuse p53 staining. Sex cord-like area, especially the solid area, showed positive staining for EMA, vimentin, α-inhibin, CD99, calretinin, p53, CD56, synaptophysin, and chromogranin A, which is a staining pattern similar to that previously reported SEC of the endometrium. Diminished membranous and positive cytoplasmic staining for β-catenin was observed. This is the first case report of an endometrial carcinosarcoma containing an SEC component. SECs of the endometrium might exhibit sex cord-like differentiation in contrast to SECs of the ovary, which do not exhibit sex cord differentiation.

Corded and Hyalinized Endometrioid Adenocarcinoma (CHEC) of the Uterine Corpus are Characterized by CTNNB1 Mutations and Can Show Adverse Clinical Outcomes

Corded and hyalinized endometrioid adenocarcinoma (CHEC) is a morphologic variant of endometrioid adenocarcinoma that is typically low-grade [International Federation of Gynecology and Obstetrics (FIGO) grade 1-2]. CHEC exhibits a biphasic appearance with gland forming adenocarcinoma merging with a diffuse component with corded growth often in a hyalinized matrix; squamous differentiation is frequent and osteoid production can be seen. This morphologic appearance can invoke a large differential diagnosis including carcinosarcoma. CHEC is thought to be associated with good clinical outcome although the available data is sparse. We performed detailed clinical, morphologic, immunohistochemical, and molecular analyses on a cohort of 7 CHEC. Six cases exhibited features of classic low-grade CHEC while one case showed greater cytologic atypia (high-grade CHEC). Patient age ranged from 19 to 69 yr. Four patients presented at stage I, 2 at stage II, and 1 at stage III. All tumors demonstrated nuclear staining for beta-catenin and loss of E-cadherin in the corded and hyalinized component. There was relative loss of epithelial markers. Loss of PTEN and ARID1A was seen in 4 and 3 tumors, respectively, and 1 tumor displayed loss of MLH1 and PMS2. Next-generation sequencing revealed CTNNB1 and PI3K pathway mutations in all 7 cases with TP53 and RB1 alterations in the high-grade CHEC. Clinical follow-up was available for 6 patients; 2 died of disease (48 and 50 mo), 2 are alive with disease (both recurred at 13 mo), and 2 have no evidence of disease (13 and 77 mo). Our study shows that CHEC universally harbors CTNNB1 mutations with nuclear staining for beta-catenin, can rarely show high-grade cytology, and can be associated with adverse clinical outcomes.

Corded and Hyalinized and Spindled Endometrioid Endometrial Carcinoma: A Clinicopathologic and Molecular Analysis of 9 Tumors Based on the TCGA Classifier

Corded and hyalinized and spindled carcinomas are rare variants of endometrioid carcinoma (EC) characterized by cords of low-grade epithelial cells (±spindle cells) within a hyalinized stroma or spindled epithelial cells, respectively, that merge with conventional low-grade EC. Due to their "biphasic" morphology, these tumors are often misdiagnosed as carcinosarcoma. The clinicopathologic features including mismatch repair protein (PMS2 and MSH6) and p53 immunohistochemical expression and POLE mutational status of 9 corded and hyalinized and spindled endometrial ECs were evaluated and classified into The Cancer Genome Atlas (TCGA) based molecular subgroups. Beta-catenin immunohistochemistry was performed as a surrogate for CTNNB1 mutational status. The mean age at diagnosis was 49 years (range: 34 to 68 y) with staging information available for 6 patients: stage IA (n=1), stage IB (n=1), stage II (n=2), stage IIIA (n=1), stage IIIC1 (n=1). A prominent corded and hyalinized component was present in 7 ECs comprising 15% to 80% of the tumor with a minor (5% to 15%) spindled morphology in 5. Two additional tumors were composed of a low-grade spindled component comprising 25% to 30% of the neoplasm. Tumors were grade 1 (n=3), grade 2 (n=5), and grade 2 to 3 (n=1) and squamous differentiation was identified in 8/9. All tumors had preserved expression of mismatch repair proteins with 8 showing a p53 wild-type phenotype including the grade 2 to 3 EC; 1 grade 2, stage IB tumor exhibited a mutant pattern of expression. All (n=7) but 1 tumor demonstrated nuclear beta-catenin expression in the glandular, squamous, and corded or spindled components. POLE exonuclease domain mutations were absent in all tumors. Based on our findings, corded and hyalinized EC and EC with spindle cells are usually low grade, low stage, and present at a younger age and exhibit squamous differentiation at an increased frequency compared to typical EC. Unlike carcinosarcomas, which frequently harbor TP53 mutations, these tumors usually exhibit wild-type p53 and nuclear beta-catenin expression, indicative of underlying CTNNB1 mutations. According to the TCGA subgroups of endometrial carcinoma, the majority of corded and hyalinized and spindled EC appear to fall into the copy number low ("no specific molecular profile") subgroup.

Mixed Endometrioid Adenocarcinoma and Müllerian Adenosarcoma of the Uterus and Ovary: Clinicopathologic Characterization With Emphasis on its Distinction From Carcinosarcoma

Mullerian adenosarcoma is a biphasic neoplasm composed of benign or atypical Müllerian epithelium and a malignant mesenchymal component that is usually, but not always, of low grade. Focal architectural or cytologic atypia of the epithelial component resembling atypical hyperplasia may uncommonly be present and foci of adenocarcinoma have been rarely reported. Whether the coexistence of these 2 tumor components is a result of independent primaries (collision tumor), adenocarcinoma arising from the epithelial component of the adenosarcoma, an unusual form of carcinosarcoma or some other mechanism is uncertain. To establish the diagnostic criteria and clinical significance of the coexistence of adenocarcinoma in close association with Müllerian adenosarcoma, we conducted a multi-institutional study of these rare tumors. Twenty-six patients were identified with "mixed" adenosarcoma and adenocarcinoma; they ranged in age from 43 to 87 years (median: 66 y). Tumors occurred in the uterine corpus (n=22), ovary (n=2), and the pelvis (n=2). All but 6 had International Federation of Gynecology and Obstetrics (FIGO) stage I disease. All extrauterine tumors were associated with endometriosis. The tumor size ranged from 2 to 25 cm (median: 7.9 cm). The sarcomatous component was of low grade in 18 and high grade in 8 (the majority demonstrating rhabdomyoblastic differentiation); 9 had stromal overgrowth. Twenty-five carcinomas were endometrioid in type (23 FIGO grade 1; 3 FIGO grade 2) and 1 carcinoma was dedifferentiated with FIGO grade 1 endometrioid adenocarcinoma component; 33% of the uterine neoplasms were associated with adjacent endometrial hyperplasia. Next-generation sequencing in 2 tumors identified similar molecular abnormalities in the sarcomatous and carcinomatous components supporting a clonal relationship. Of 10 patients with available follow-up (median: 18 mo), 8 had no evidence of disease and 2 died of recurrent sarcoma at 7 and 8 months. Endometrioid adenocarcinomas that arise in close spatial association with Müllerian adenosarcoma appear to be clonally related to the sarcoma. Unlike carcinosarcomas, these tumors are usually early stage at presentation. The prognosis appears to be driven by the sarcomatous component. These tumors should be distinguished from carcinosarcomas, dedifferentiated endometrial carcinomas, and corded and hyalinized endometrioid carcinomas.

Hyalinized stroma is a characteristic feature of pancreatic intraductal oncocytic papillary neoplasm: An immunohistochemical study

Hyalinized stroma (HS) is a dense, eosinophilic, and amorphous extracellular material in the stroma. HS is observed in several tumors; however, it has not been comprehensively studied in pancreatic intraductal papillary mucinous neoplasm (IPMN) or intraductal oncocytic papillary neoplasm (IOPN). Here, we aimed to evaluate the immunohistochemical and microscopic characteristics of HS in IPMN and IOPN. The prevalence of HS was determined in 168 cases of IPMN, including intestinal type (IPMN-I), gastric type (IPMN-G), and pancreatobiliary type (IPMN-PB), as well as in 11 cases of IOPN. Immunohistochemical staining for laminin and collagen (types I, II, III, IV, and V), as well as Congo red staining were performed in IPMN and IOPN cases containing HS. The prevalence of HS among the IPMN and IOPN specimens was 1.2% (2/168 cases) and 45.5% (5/11 cases), respectively. The prevalence rates of HS in each IPMN subtype were as follows: 2.2% (2/91 cases) in IPMN-G, and 0% in IPMN-PB and IPMN-I. All seven HS cases were positive for collagen I, III, IV, and V but were negative for Congo red staining. Most cases showed negative, focal, or weak expression of laminin and type II collagen. These findings indicate that HS is associated with IOPN and is primarily composed of collagen fibers.

Endometriosis-related pathology: a discussion of selected uncommon benign, premalignant and malignant lesions

Endometriosis is an extremely common condition and, in most cases, establishing a histological diagnosis is straightforward, although a variety of benign alterations may result in problems with interpretation. In this review, I discuss selected uncommon variants of endometriosis or benign alterations that may result in diagnostic problems. The topics covered include the contentious issue of so-called atypical endometriosis, stromal endometriosis, polypoid endometriosis, and the association of endometriosis with florid mesothelial hyperplasia. The propensity of endometriosis to undergo neoplastic transformation (especially to endometrioid and clear cell carcinoma) is well known. Selected issues relating to the various neoplasms that can arise in endometriosis are discussed, with a particular concentration on unusual variants of endometrioid carcinoma that result in a disproportionately high number of issues in referral practice. The propensity of ovarian endometrioid carcinomas to show an unexpected ('aberrant') immunophenotype with positive staining with 'intestinal' markers and negative staining with Mullerian markers is also discussed. Uncommon tumour types that may arise in endometriosis, namely seromucinous neoplasms, mesonephric-like carcinomas, and somatically derived yolk sac tumours, are also covered.

Uterine Tumor Resembling Ovarian Sex Cord Tumor (UTROSCT): A Morphologic and Molecular Study of 26 Cases Confirms Recurrent NCOA1-3 Rearrangement

Uterine tumor resembling ovarian sex cord tumor (UTROSCT) is a rare mesenchymal neoplasm, of uncertain biological potential, that was recently reported to exhibit recurrent gene fusions involving NCOA2-3. The purpose of this study was to, using a larger sample size, better characterize the histopathologic and molecular diversity of UTROSCT. Twenty-six cases of UTROSCT from 5 institutions were selected for further study. Fluorescence in situ hybridization for NCOA1, NCOA2, NCOA3, ESR1 and GREB1, and targeted RNA sequencing was performed on 17 and 8 UTROSCTs, respectively. Eight cases underwent massively parallel sequencing to detect single nucleotide variants (SNV), copy number variations, and structural variants using a targeted hybrid-capture based assay. NCOA1-3 rearrangement was identified in 81.8% (18/22) of cases. The most common fusion was ESR1-NCOA3, occurring in 40.9% (9/22). GREB1-NCOA1 (n=4), ESR1-NCOA2 (n=3), and GREB1-NCOA2 (n=1) rearrangements were also identified. No recurrent SNVs were identified and no tumor had SNVs in FOXL2, DICER1, STK11, or AKT1, which can be seen in ovarian sex cord-stromal tumors. Copy number variations were infrequent. Clinical follow-up was available for 11 cases with a mean follow-up interval of 94.4 (range, 1 to 319) months. Only one case had a recurrence 66 months after the initial diagnosis and this was the single case with a GREB1-NCOA2 fusion. This study reports the morphologic spectrum of UTROSCT and confirms the recently reported recurrent NCOA2-3 gene fusions, in addition to identifying novel rearrangements involving NCOA1 in these tumors.

Uterine Mesenchymal Tumors: Update on Classification, Staging, and Molecular Features

The spectrum of mesenchymal neoplasia in the uterus has expanded in recent years. First, the identification of prevalent, recurrent molecular alterations has led to a more biologically and clinically congruent classification of endometrial stromal tumors. Likewise, the diagnostic criteria of several rare and miscellaneous tumor types have been refined in recent case series (Perivascular Epithelioid Cell tumor, inflammatory myofibroblastic tumor). Pure mesenchymal tumors are still broadly classified based on morphology according to the tumor cell phenotype. Smooth muscle tumors predominate in frequency, followed by tumors of endometrial stromal derivation; the latter are covered in depth in this article with an emphasis on defining molecular alterations and their morphologic and clinical correlates. The remaining entities comprise a miscellaneous group in which cell derivation does not have a normal counterpart in the uterus (eg, rhabdomyosarcoma) or is obscure (eg, undifferentiated uterine sarcoma). This article discusses their clinical relevance, recent insights into their molecular biology, and the most important differential diagnoses. Regarding the latter, immunohistochemistry and (increasingly) molecular diagnostics play a role in the diagnostic workup. We conclude with a few considerations on intraoperative consultation and macroscopic examination, as well as pathologic staging and grading of uterine sarcomas as per the most recent American Joint Cancer Commission and the Fédération Internationale de Gynécologie et d'Obstétrique staging systems.

Uterine lesions with sex cord-like architectures: a systematic review

Background

Sex cord-like elements are rarely observed in uterine lesions, but these morphological patterns could appear in a variety of uterine tumors and non-tumorous lesions. In this review, we collected the literatures regarding the uterine tumorous and non-tumorous lesions containing sex cord-like elements and summarized these lesions in terms of clinicopathological, immunohistochemical, and molecular features in order to further understand these lesions and provide some new ideas for differential diagnosis.

Main body

This section provides a comprehensive overview of the clinicopathological, immunohistochemical, and molecular features of uterine lesions with sex cord-like architectures including uterine tumors resembling ovarian sex cord tumors, endometrial stromal tumors, adenomyosis, endometrial polyps, leiomyoma, epithelioid leiomyosarcoma, adenosarcoma, sertoliform endometrioid carcinoma, corded and hyalinized endometrioid carcinoma, mesonephric adenocarcinoma, and mesonephric-like adenocarcinoma. The differential diagnosis based on morphology, immunohistochemistry, and molecular alterations has also been discussed.

Conclusion

The sex cord-like areas in these lesions show heterogeneous but similar morphological features. Additionally, immunohistochemical staining plays a limited role in differential diagnosis. Furthermore, it is of significance for pathologists to better understand these lesions in order to avoid confusion and mistakes during pathological diagnosis, especially in a biopsy/curettage specimen.

Endometrial Carcinoma Diagnosis: Use of FIGO Grading and Genomic Subcategories in Clinical Practice: Recommendations of the International Society of Gynecological Pathologists

In this review, we sought to address 2 important issues in the diagnosis of endometrial carcinoma: how to grade endometrial endometrioid carcinomas and how to incorporate the 4 genomic subcategories of endometrial carcinoma, as identified through The Cancer Genome Atlas, into clinical practice. The current International Federation of Gynecology and Obstetrics grading scheme provides prognostic information that can be used to guide the extent of surgery and use of adjuvant chemotherapy or radiation therapy. We recommend moving toward a binary scheme to grade endometrial endometrioid carcinomas by considering International Federation of Gynecology and Obstetrics defined grades 1 and 2 tumors as "low grade" and grade 3 tumors as "high grade." The current evidence base does not support the use of a 3-tiered grading system, although this is considered standard by International Federation of Gynecology and Obstetrics, the American College of Obstetricians and Gynecologists, and the College of American Pathologists. As for the 4 genomic subtypes of endometrial carcinoma (copy number low/p53 wild-type, copy number high/p53 abnormal, polymerase E mutant, and mismatch repair deficient), which only recently have been identified, there is accumulating evidence showing these categories can be reproducibly diagnosed and accurately assessed based on biopsy/curettage specimens as well as hysterectomy specimens. Furthermore, this subclassification system can be adapted for current clinical practice and is of prognostic significance independent of conventional variables used for risk assessment in patients with endometrial carcinoma (eg, stage). It is too soon to recommend the routine use of genomic classification in this setting; however, with further evidence, this system may become the basis for the subclassification of all endometrial carcinomas, supplanting (partially or completely) histotype, and grade. These recommendations were developed from the International Society of Gynecological Pathologists Endometrial Carcinoma project.

Issues in the Differential Diagnosis of Uterine Low-grade Endometrioid Carcinoma, Including Mixed Endometrial Carcinomas: Recommendations from the International Society of Gynecological Pathologists

This article provides practical recommendations developed from the International Society of Gynecological Pathologists Endometrial Carcinoma Project to address 4 issues that may arise in the diagnosis of uterine corpus low-grade endometrioid carcinoma: (1) The distinction between atypical hyperplasia and low-grade endometrioid carcinoma. (2) The distinction between low-grade endometrioid carcinoma and serous carcinoma. (3) The distinction between corded and hyalinized or spindle cell variants of low-grade endometrioid carcinoma and carcinosarcoma. (4) The diagnostic criteria for mixed endometrial carcinomas, a rare entity that should be diagnosed only after exclusion of a spectrum of tumors including morphologic variants of endometrioid carcinoma, dedifferentiated endometrial carcinoma, carcinosarcoma, and endometrial carcinomas with ambiguous morphology.

Corded and hyalinized mesonephric-like adenocarcinoma of the uterine corpus: report of a case mimicking endometrioid carcinoma

Mesonephric-like adenocarcinoma is a recently described adenocarcinoma of the uterine body and ovary with overlapping features of mesonephric adenocarcinoma and endometrioid carcinoma. It is thought to be a mullerian adenocarcinoma that has differentiated along mesonephric lines. A 71-year-old woman had a 3-cm endometrial mass that invaded the myometrium without gross or microscopic evidence of cervical involvement. The tumor had a variety of architectural patterns and produced prominent stromal hyalinization containing embedded cords and trabeculae of tumor cells. No squamous or mucinous differentiation or associated mesonephric remnants or hyperplasia was identified. The tumor was positive for TTF1 and GATA3, very focally and weakly positive for estrogen receptor and negative for progesterone receptor and nuclear expression of β-catenin. An unusual inverse pattern of TTF1 and GATA3 immunoreactivity was observed. DNA analysis by digital droplet polymerase chain reaction and quantitative polymerase chain reaction identified an activating KRAS (G12A) mutation. The tumor was interpreted as corded and hyalinized mesonephric-like adenocarcinoma that mimicked corded and hyalinized endometrioid carcinoma.

Endometrioid Endometrial Carcinoma With Spindle Cells-Aberrant p16 and p53 Expression

Endometrioid carcinoma is known for its diverse morphology and may pose a diagnostic dilemma when it presents with a spindle cell component. We present a case of a 65-year-old woman with postmenopausal bleeding. Physical examination showed a mass protruding from the external cervical os. The patient underwent biopsy followed by hysterectomy. Pathologic examination showed an endometrioid endometrial carcinoma with spindle cell differentiation arising in an endometrial polyp, which raised a variety of differential diagnoses. Prior reports of this tumor type showed nonaberrant immunohistochemical expression of p16 and p53. However, this case showed p16 and p53 overexpression indicating that there is a spectrum of these tumors.

Evolving Roles of Histologic Evaluation and Molecular/Genomic Profiling in the Management of Endometrial Cancer

Endometrial cancers are the most common gynecologic malignancies. The staging of endometrial cancer has evolved from a clinical-based system to a comprehensive surgical-pathologic approach that allows for better risk stratification and treatment planning. Over the past few years, use of NCCN's sentinel lymph node (SLN) mapping algorithm for the surgical staging of endometrial cancer has gained significant acceptance and is now commonly applied in many practices. However, pathologic evaluation of prognostic factors is beset by challenges, including the reproducibility of histologic classification and FIGO's grading, as well as the questionable clinical significance of low-volume tumor in SLNs. With the revelation of major genomic classes of endometrial cancer comes the potential for improved, reproducible, and prognostically relevant classification schemes, which integrate traditional pathologic parameters with genomic findings, to aid in treatment decisions. Pathologic identification of new variants of endometrial cancer, such as undifferentiated carcinoma, continues to advance the phenotypic spectrum of these tumors, spurring genomic and functional studies to further characterize their mechanistic underpinnings and potentially reveal new avenues for treatment. In the era of precision medicine, pathologic assessment of biomarkers (eg, mismatch repair proteins) and recognition of phenotypes that are amenable to specific targeted therapies (such as POLE-mutated tumors) have become integral to the management of women with endometrial carcinoma.

Endometrial Endometrioid Carcinoma With Large Cystic Growth Configuration and Deceptive Pattern of Invasion Associated With Abundant Nodular Fasciitis-like Stroma: A Unique Hitherto Unreported Histology in Endometrioid Carcinoma

We describe a case of an unusual endometrial endometrioid carcinoma occurring in a 67-year-old woman. The tumor involved uterine corpus as well as lower uterine segment and presented as polypoid tumor protruding through the cervical orifice. Microscopically, the tumor was characterized by broad zones of cytologically bland fibromyxoid stroma resembling nodular fasciitis, showing vaguely nodular architecture. Neoplastic glands were characterized by interconnected elongated slit-like and large cystic profiles, mostly lined by flattened epithelium with variable squamous differentiation, whereas typical columnar endometrioid cells were only focally present. Voluminous nodules of the stroma produced phyllodes-like appearance of the tumor. The tumor showed some resemblance to the microcystic, elongated, and fragmented (MELF) glands growth pattern, but in contrast with MELF pattern, where fibromyxoid change occurs focally, in the presented case abundant myofibroblastic proliferation was present throughout the tumor and the neoplastic glands showed anastomosing "large cystic" rather than "small cystic" profiles. Some of the neoplastic glands presented almost complete or complete squamous differentiation, with relatively bland-looking squamous cells and no hint of endometrioid differentiation, which resulted in initial misdiagnosis of Müllerian adenofibroma. We believe that nodular fasciitis-like pattern represents yet undescribed, and diagnostically challenging pattern of invasion in endometrial endometrioid carcinoma.

A practical approach to the diagnosis of mixed epithelial and mesenchymal tumours of the uterus

The current 2014 World Health Organization (WHO) Classification of mixed epithelial and mesenchymal tumours of the uterus includes categories of carcinosarcoma, adenosarcoma, adenofibroma, adenomyoma and atypical polypoid adenomyoma, the last two lesions being composed of an admixture of benign epithelial and mesenchymal elements with a prominent smooth muscle component. In this review, each of these categories of uterine neoplasm is covered with an emphasis on practical tips for the surgical pathologist and new developments. In particular, helpful clues in the distinction between carcinosarcoma and dedifferentiated endometrial carcinoma will be discussed. In addition, salient features to help distinguish between adenofibroma, adenosarcoma, embryonal rhabdomyosarcoma and other mesenchymal neoplasms in the differential diagnosis will be outlined. Finally, a discussion of adenomyoma and its main differential diagnostic considerations will be covered.

How to approach the many faces of endometrioid carcinoma

This article reviews the salient features of variants of endometrioid carcinoma (ECa) that can pose a diagnostic challenge and/or are associated with unique clinicopathological findings. Variants with distinct architectural and cytologic features include the following: (1) ECa with a villoglandular pattern (tumor with finger-like papillae lined by bland cells with a tendency for vascular/lymphatic invasion and lymph node metastasis once this pattern is seen within the myoinvasive component); (2) papillary ECa of intermediate grade (grade 2) (tumor that can be mistaken for serous carcinoma, as it contains papillae showing slightly irregular contours, moderately atypical cells, and it is associated with vascular/lymphatic invasion/lymph node metastasis, but with common association with mucinous metaplasia, MELF (microcystic, elongated, and fragmented) pattern of invasion, and wild p53 expression); (3) ECa with non-villous papillae (tumor containing pseudopapillae within glands with bland-appearing cytology commonly associated with abortive squamous differentiation and otherwise not different from usual ECa); (4) ECa with microglandular-like pattern (tumor that mimics microglandular hyperplasia of the cervix, often lacking the typical appearance of microglandular hyperplasia and showing Ki-67 index >10%, strong CD10 expression, and negative PAX-2, p63, and CD34); and (5) ECa with sex cord-like formations and hyalinization (tumor with interconnected cords and nests of bland epithelioid and spindled cells that merge with a typical component of low-grade ECa, usually associated with squamous differentiation and hyalinization). This tumor should be distinguished from carcinosarcoma and, in contrast to the latter, it shows nuclear β-catenin expression, ER/PR and patchy p16 positivity, tends to present at a low stage, and has a favorable prognosis and (6) dedifferentiated ECa (tumor showing a low-grade ECa juxtaposed to an undifferentiated carcinoma-the latter characterized by variably sized monotonous, often non-cohesive cells with brisk mitotic activity and usually arranged in sheets). Undifferentiated carcinoma tends to be negative for PAX8 and ER/PR with variable expression of keratins and can be associated with microsatellite instability (may be part of Lynch syndrome). Variants with distinct cytological features include the following: (1) ECa with clear cells (tumors with clearing due to 'clear' (glycogenated) squamous cells, distinct vacuoles, or not otherwise specified. EC with clear cells should be distinguished from clear cell carcinoma by the absence of the variety of architectural patterns, lack of cuboidal/flattened/hobnail cells, and lack of degree of atypia usually detected in clear cell carcinoma. In addition, they are ER/PR positive and Napsin A and p504S negative in contrast to clear cell carcinoma); (2) ECa with spindle cells (tumor with transition from spindle cells to the glandular component of a low-grade ECa. The spindle cells are keratin, ER/PR, and patchy p16 positive and show wild-type p53 expression); (3) ECa with mucinous differentiation (this tumor can be mistaken for a cervical adenocarcinoma, as they have overlapping features. Expression of ER/PR and vimentin in the context of a negative or patchy p16 positivity and the absence of high-risk HPV allows a correct diagnosis).

In-depth molecular profiling of the biphasic components of uterine carcinosarcomas

Uterine carcinosarcoma is a clinically aggressive malignancy composed of a mix of carcinomatous and sarcomatous elements. We performed targeted next-generation sequencing of 27 uterine cancer and sarcoma genes together with immunohistochemical analyses of selected proteins in 30 uterine carcinosarcomas. This included 13 cases in which the distinct carcinoma and sarcoma components were sequenced separately and 10 cases where the metastatic tumours were analysed in addition to the primary tumours. We identified non-synonymous somatic mutations in 90% of the cases, with 27 of 30 cases (90%) harbouring TP53 alterations. The PI3K pathway was the most commonly mutated signalling pathway with mutations identified in PIK3CA, PTEN, PIK3R1, and/or PIK3R2 in two-thirds of the cases. Mutations in FBXW7, PPP2R1A, ARID1A and KRAS were demonstrated in a minority of cases. In cases where the carcinomatous and sarcomatous components were separately analysed, most of the mutations identified were present in both components, indicating a common origin for the two components. Furthermore, the same TP53 alterations and/or PI3K pathway mutations seen in the primary tumours were also identified in the metastatic sites. Overall, carcinosarcomas exhibited heterogeneous molecular features that resemble the heterogeneity seen in endometrial carcinomas, with some showing endometrioid carcinoma-like and others showing serous carcinoma-like mutation profiles. While patients with serous-like tumours presented more frequently with advanced-stage disease compared to patients with endometrioid-like tumours, there was no statistical difference in outcome between the two groups. Our results provide insights into the oncogenesis of uterine carcinosarcoma and identify targetable mutations that represent early oncogenic events. The findings of the different molecular types of uterine carcinosarcoma that parallel the different molecular types in endometrial carcinoma may have future treatment implications with targeted therapies.

The Utility of Immunohistochemistry in the Differential Diagnosis of Gynecologic Disorders

Context

Immunohistochemistry has assumed an increasing role in the identification and characterization of gynecologic disorders including lesions with deceptively bland morphology, uncommon and underdiagnosed neoplasms, and neoplasms with specific genetic alterations associated with overexpression or loss of expression of specific proteins. The diagnostic accuracy has been significantly improved owing to the discovery and increasing experience with the tumor-associated biomarkers, and the increasing demand for precise tumor classification to assess suitability for the expanding therapeutic modalities including clinical trials.

Objective

To differentiate lesions of the gynecologic tract through the use of effective immunohistochemical panels.

Data Sources

Literature review and authors' personal practice experience.

Conclusions

The application of diagnostic and prognostic immunohistochemical panels has enabled pathologists to better guide therapeutic decisions and to better predict the clinical outcome. It is now well established that the use of ancillary testing, including immunohistochemistry, has a significant power in the identification, differentiation, and classification of reactive, premalignant, and malignant gynecologic disorders. This article discusses the utilities and pitfalls of the commonly used immunohistochemical markers in the context of overlapping morphologic features encountered in the uterus, ovaries, and fallopian tubes.

Immunohistochemical characterization of endometrial carcinomas: endometrioid, serous and clear cell adenocarcinomas in association with genetic analysis

Developments in immunohistochemistry, which are closely linked with the advances in the analyses of genetic abnormalities and their associated molecular disorders as early and late histogenetic events, have contributed greatly to the improvement of pathological diagnostic confirmation and validation. Immunohistochemistry has also generated great benefit to the innovation of therapeutic strategies for various kinds of cancers. In this article, the three representative histological types of corpus cancer, namely, endometrioid adenocarcinoma, serous adenocarcinoma and clear cell adenocarcinoma, will be histologically approached in association with their immunohistochemical profiles as well as genetic disorders. First, the focus will be on 'Conventional/prototypic features,' followed by 'Controversy over conventional histological subclassification,' and subsequently 'Tumorigenesis and re-subclassification'.

Myoepithelioma of the ovary: first reported case

A wide variety of neoplasms of varying histogenesis occur within the ovary. We report the first case of a primary ovarian myoepithelioma, a diagnosis made on the basis of the morphologic features coupled with immunoreactivity with epithelial and myoid markers. The tumor had a lobulated appearance with variable architectural patterns including anastomosing cords, trabeculae, and nests of epithelioid to spindled tumor cells within a hyalinised and focally myxoid stroma. Fluorescence in situ hybridization for EWS gene rearrangement and reverse transcriptase polymerase chain reaction for EWSR1-POU5F1 and EWSR1-PBX1, molecular abnormalities which are found in some extrasalivary myoepitheliomas, were negative. In reporting this unique neoplasm, we discuss the wide differential diagnosis generated by the case.

Ovarian serous carcinoma associated with a distinct "corded and hyalinized" pattern

The "corded and hyalinized" pattern, described in endometrioid carcinoma, has not been previously reported in association with serous carcinoma. We describe a unique case of serous neoplasm of low malignant potential with low-grade serous carcinoma combined with a distinct pattern of high-grade carcinoma characterized by cords of epithelioid and spindled cells enmeshed in a hyalinized, collagenous stroma. This pattern was the predominant architecture in the patient's recurrence and caused a diagnostic challenge, as the splenic recurrence was initially diagnosed as a second primary high-grade spindle cell neoplasm. Both ovarian and splenic tumors displayed positive immunohistochemical staining for cytokeratin 7, cytokeratin 8/18, estrogen receptor, and paired box gene 8 (PAX-8) in the conventional serous carcinoma and the corded and hyalinized component, confirming the diagnosis of recurrent carcinoma. The behavior in this unique case of serous carcinoma associated with a distinct corded and hyalinized pattern was more aggressive than low-grade serous carcinoma, but more favorable than malignant mixed mullerian tumor.

KRAS mutations in ovarian low-grade endometrioid adenocarcinoma: association with concurrent endometriosis

The association between ovarian endometrioid adenocarcinoma and endometriosis is well established. However, not all endometrioid adenocarcinomas are directly related to endometriosis, and it has been suggested that there may be clinicopathologic differences between endometriosis-positive and endometriosis-negative tumors. Molecular alterations in endometrioid adenocarcinoma include KRAS and BRAF mutations, but the incidence of these abnormalities in previous reports has been highly variable (0%-36% and 0%-24%, respectively). This may be explained by relatively small sample sizes in earlier studies but could also reflect difficulties in accurately classifying high-grade ovarian malignancies. In the current study, we investigated KRAS and BRAF mutations in 78 low-grade (FIGO grade 1 and 2) endometrioid adenocarcinomas and compared the results with the presence of endometriosis in the tumor-associated ovary and/or in other pelvic sites. KRAS mutations were identified in 12 (29%) of 42 endometriosis-associated endometrioid adenocarcinomas with satisfactory analysis but in only 1 (3%) of 29 tumors in which endometriosis was not identified. BRAF mutation was identified only in a single endometriosis-associated case. These findings support the hypothesis that endometriosis-associated and independent endometrioid adenocarcinoma may develop via different molecular pathways and that KRAS mutations have an important role only in the former tumors. In contrast, BRAF mutations do not appear to have a significant role in either endometrioid adenocarcinoma subgroup. This may be relevant to future targeted therapies in patients with high-stage or recurrent disease and indicate that histopathologists should carefully examine endometrioid adenocarcinoma specimens, including nonneoplastic tissues, for the presence of endometriosis.

WT1 expression in the female genital tract

The Wilms tumor gene 1 (WT1) has been reported in normal tissues and many neoplasms of the female genital tract. This review discusses WT1 expression in the female genital tract and its potential utility in the differential diagnosis of neoplasms that occur at this location. WT1 is of value in the differential diagnosis of synchronous serous carcinomas arising in the ovary/fallopian tube/peritoneum and endometrium, as strong WT1 positivity in both tumors points toward an extrauterine origin. In addition, WT1 can be used to distinguish sex cord stromal tumors (WT1 positive) from endometrioid carcinomas (OECs). WT1 expression is not helpful in the differential diagnosis of ovarian serous carcinomas (OSCs) and transitional carcinomas, as both are typically positive and has limited value in the distinction of serous tumors arising in the ovary/fallopian tube/peritoneum from mesotheliomas. WT1 is also not helpful to differentiate small cell carcinoma of hypercalcemic type from juvenile granulosa cell tumor, a common diagnostic problem. Intra-abdominal desmoplastic round cell tumor reacts to WT1 (C-terminal) in contrast to all other tumors discussed which helps to separate this rare tumor from most other small round cell tumors that may involve, primarily or secondarily, the ovary with the exception of small cell carcinoma of hypercalcemic type that typically reacts with the N-terminal of WT1.