A Combined Morphologic and Molecular Approach to Retrospectively Identify KRAS-Mutated Mesonephric-like Adenocarcinomas of the Endometrium

[Endometrial carcinomas in 2021: What to say and what to do?]

The treatment of endometrial carcinomas relies on histopathological data such as tumor type, grade, stage, and lymphovascular invasion. We herein present the recent advances in the pathological appreciation of these criteria, relying in the last 2020 WHO classification of female genital tumours. Furthermore, molecular typing of endometrial carcinoma has become a rule with strong prognostic and therapeutic implications. The TP53-mutated/serous-like and hypermutated/dMMR groups can be easily identified by the pathologist using immunohistochemistry. The ultramutated/POLE-mutated group identification requires sequencing technologies. We herein explain how easily incorporate this novel histomolecular classification, now included in scholarly society recommendations, in the pathologist routine.

Extrauterine Mesonephric-like Neoplasms: Expanding the Morphologic Spectrum

Mesonephric-like adenocarcinomas (MLA) are rare neoplasms arising in the uterine corpus and ovary which have been added to the recent 2020 World Health Organization Classification of Female Genital Tumors. They have similar morphology and immunophenotype and exhibit molecular aberrations similar to cervical mesonephric adenocarcinomas. It is debated as to whether they are of mesonephric or Mullerian origin. We describe the clinical, pathologic, immunohistochemical, and molecular features of 5 cases of extrauterine mesonephric-like proliferations (4 ovary, 1 extraovarian), all with novel and hitherto unreported features. These include an origin of MLA in extraovarian endometriosis, an association of ovarian MLA with high-grade serous carcinoma, mixed germ cell tumor and mature teratoma, and a borderline ovarian endometrioid tumor exhibiting mesonephric differentiation. Four of the cases exhibited a KRAS variant and 3 also a PIK3CA variant. In reporting these cases, we expand on the published tumor types associated with MLA and report for the first time a borderline tumor exhibiting mesonephric differentiation. We show the value of molecular testing in helping to confirm a mesonephric-like lesion and in determining the relationship between the different neoplastic components. We provide further evidence for a Mullerian origin, rather than a true mesonephric origin, in some of these cases. We also speculate that in the 2 cases associated with germ cell neoplasms, the MLA arose out of the germ cell tumor.

Atypical Mesonephric Hyperplasia of the Uterus Harbors Pathogenic Mutation of Kirsten Rat Sarcoma 2 Viral Oncogene Homolog (KRAS) and Gain of Chromosome 1q

BACKGROUND/AIM

Mesonephric carcinoma (MNC) is a rare but notable entity of the female genital tract. While many researchers have acknowledged and studied MNC, much remains unknown on the characteristics of mesonephric remnant (MNR) or hyperplasia (MNH). There has not been any study examining the molecular features of MNR and MNH so far. The aim of this study was to investigate the clinicopathological and molecular characteristics of ten uterine mesonephric lesions, including two MNRs without atypia, four MNHs without atypia, and three MNHs with atypia.

MATERIALS AND METHODS

We reviewed the electronic medical records and all available slides of ten cases from multiple institutions. Targeted sequencing and array comparative genomic hybridization were performed.

RESULTS

Three atypical MNHs displayed nuclear enlargement, mild-to-moderate nuclear pleomorphism, and nuclear membrane irregularity, and harbored pathogenic Kirsten rat sarcoma 2 viral oncogene homolograt sarcoma 2 viral oncogene homolog (KRAS) mutation. Two of those that co-existed with MNC harbored the same sequence alterations as each of their adjacent MNC. One of the three atypical MNHs harbored chromosome 1q gain.

CONCLUSION

Atypical MNH is a potential premalignant lesion in which KRAS mutation and chromosome 1q gain play an important role in the early stage of mesonephric carcinogenesis.

Mesonephric Adenocarcinoma of the Uterine Corpus: A Report on 2 Cases With Comparison to Its Cervical Counterpart

Mesonephric adenocarcinoma (MA) is a rare tumor of the female genital tract that develops in the uterine cervix. Recently, a few cases of MA arising from the uterine body have been reported, whereas the differences between these 2 entities remain unknown. Two uterine MAs and 1 cervical MA were included in this study. In uterine MA, there was an admixture of various growth patterns with tubular, glandular, slit-like, papillary, and solid architectures. Both tumors extensively involved the endometrium, while no mesonephric remnants were noted. Immunostaining was diffusely positive for TTF-1, while there was only focal staining for GATA3. KRAS somatic mutation was present in both uterine cases. In cervical MA, the tumor also had different growth patterns but no endocervical mucosa involvement. A residual mesonephric duct was present. GATA3 showed diffuse staining, but TTF-1 was totally negative. Therefore, uterine MA was not entirely consistent with its cervical counterpart in both morphologic characteristics and immunostaining.

Serous Carcinoma of the Endometrium with Mesonephric-Like Differentiation Initially Misdiagnosed as Uterine Mesonephric-Like Adenocarcinoma: A Case Report with Emphasis on the Immunostaining and the Identification of Splice Site TP53 Mutation

We present herein a rare case of uterine serous carcinoma with mesonephric-like differentiation (SC-MLD) initially misdiagnosed as mesonephric-like adenocarcinoma (MLA). A 51-year-old woman underwent total hysterectomy for a uterine tumor. Histologically, the tumor exhibited various architectures, including papillary, glandular, tubular, cribriform, and cystic. On the basis of this architectural diversity accompanied by intraluminal eosinophilic secretions and intermediate-grade nuclear atypia, the initial diagnosis was MLA. However, the tumor was diffusely and strongly positive for the expression of p16 and negative for the expression of GATA-binding protein 3 (GATA3). Furthermore, we identified a pathogenic tumor protein 53 (TP53) mutation affecting an acceptor splice site in intron 9, despite a wild-type p53 immunostaining pattern. The observations of diffuse and strong p16 expression, lack of GATA3 expression, pathogenic TP53 mutation, and wild-type Kirsten rat sarcoma viral oncogene homolog indicate that this tumor was not an MLA but an SC-MLD. Both uterine SC and MLA can exhibit various histological growth patterns. Our comprehensive clinicopathological and molecular analyses can serve to improve the understanding of this rare condition and help pathologists in making an accurate diagnosis.

[Current WHO classification of the female genitals : Many new things, but also some old]

The new WHO classification of tumors of the female genitalia entails some changes, especially those of prognostic and therapeutic relevance: there is a return to the term borderline tumor. Implants are again subdivided into noninvasive implants of the epithelial or desmoplastic type as before. Invasive extraovarian implants are classified as low-grade serous carcinoma (LGSC). Former seromucinous carcinomas are now classified as endometrioid carcinomas (seromucinous subtype). New entities of ovarian carcinomas are mesonephric-like adenocarcinoma, undifferentiated and dedifferentiated carcinoma, and mixed carcinoma. The classification of neuroendocrine neoplasms is analogous to that of pulmonary and gastrointestinal neuroendocrine neoplasms, regardless of their location. Endometrioid endometrial carcinoma can be classified into four molecular subtypes, which have significant prognostic significance. New subtypes include mucinous carcinoma of the intestinal type and mesonephric-like adenocarcinoma. Stromasarcomas of the endometrium are further subclassified based on specific molecular alterations. Adenocarcinomas (ACs) and squamous cell carcinomas (PECs) of the lower female genital tract are distinguished from HPV-associated and HPV-independent carcinomas. Block-like staining for p16 is the accepted surrogate immunohistochemical marker. Grading has not been reported for PEC. For HPV-associated AC of the cervix uteri, prognostic assessment is based on the pattern of invasion (so-called Silva pattern). Serous carcinomas in the cervix uteri are endometrial carcinomas with cervical infiltration.

Clinicopathologic Characteristics of Mesonephric Adenocarcinomas and Mesonephric-like Adenocarcinomas in the Gynecologic Tract: A Multi-institutional Study

Mesonephric adenocarcinoma (MA) and mesonephric-like adenocarcinoma (MLA) are uncommon neoplasms of the gynecologic tract that have until recently been poorly understood. Although their morphologic, immunohistochemical, and molecular profiles have been recently defined, little is known about their clinical behavior. Small studies have demonstrated inconsistent findings and no large studies have examined the clinical behavior of these adenocarcinomas. In this multi-institutional study, representing the largest and most stringently defined cohort of cases to date, we examined the clinicopathologic features of 99 MAs and MLAs (30 MAs of the uterine cervix, 44 MLAs of the endometrium, and 25 MLAs of the ovary). Only tumors with characteristic mesonephric morphology and either immunohistochemical or molecular support were included. Our results demonstrate that the majority of mesonephric neoplasms presented at an advanced stage (II to IV) (15/25 [60%] MA of the cervix, 25/43 [58%] MLA of the endometrium, and 7/18 [39%] MLA of the ovary). The majority (46/89 [52%] overall, 12/24 [50%] MA of the cervix, 24/41 [59%] MLA of the endometrium, and 10/24 [42%] MLA of the ovary) developed recurrences, most commonly distant (9/12 [75%] MA of the cervix, 22/24 [92%] MLA of the endometrium, and 5/9 [56%] MLA of the ovary). The 5-year disease-specific survival was 74% (n=26) for MA of cervix, 72% (n=43) for MLA of endometrium, and 71% (n=23) for MLA of ovary. Our results confirm that mesonephric neoplasms are a clinically aggressive group of gynecologic carcinomas that typically present at an advanced stage, with a predilection for pulmonary recurrence.

Mesonephric-Like Adenocarcinoma of the Endometrium: Diagnostic Advances to Spot This Wolf in Sheep's Clothing. A Review of the Literature

Mesonephric-like adenocarcinoma is a recently described rare neoplasm occurring in the uterine corpus and ovary. This under-recognized subtype of carcinoma can be very challenging to diagnose. In mesonephric adenocarcinoma a variety of growth patterns can be present within the same tumor, as a result of which they can be misinterpreted and diagnosed as low-grade endometrioid adenocarcinoma, clear cell carcinoma, or even serous carcinoma and carcinosarcoma. We report a case of mesonephric-like adenocarcinoma misdiagnosed as a low-grade endometrioid endometrial adenocarcinoma that had an early local recurrence and metastasized to the liver and the lungs. Histopathological, immunohistochemical and molecular analysis were performed and compared to published literature, providing a comprehensive overview of the current knowledge. Databases (Pubmed, Web of Science, Google Scholar) were searched with a combination of the following search terms: mesonephric-like, mesonephric, adenocarcinoma, carcinoma, uterine body, uterine corpus, endometrium. Mesonephric-like adenocarcinoma is a difficult-to-diagnose entity. Advanced diagnostics, including improved morphologic, immunohistochemical and molecular knowledge can help develop new therapeutic strategies against this specific subtype of endometrial cancer with an aggressive clinical behavior.

Endometrial carcinoma: molecular subtypes, precursors and the role of pathology in early diagnosis

Endometrial carcinoma (EC) is classified into a wide range of morphological variants; this list has expanded over the past decade with the inclusion of mesonephric-like and dedifferentiated carcinoma as EC variants in the fifth edition of the WHO Classification of Female Genital Tumours, and recognition that carcinosarcoma is a biphasic carcinoma rather than a sarcoma. Each EC variant has distinct molecular abnormalities, including TCGA-based molecular subtypes, allowing further subclassification and adding complexity. In contrast to this rapid progress in understanding EC, there are only two recognized EC precursor lesions: endometrial atypical hyperplasia/endometrioid intraepithelial neoplasia (EAH/EIN) and serous intraepithelial carcinoma, a situation that has not changed for many years. Diagnosis of EC precursors is a cornerstone of surgical pathology practice, with early diagnosis contributing to the relatively favorable prognosis of EC. In this review we relate the precursor lesions to each of the EC morphological variants and molecular subtypes, discuss how successful early diagnosis is for each variant/molecular subtype and how it might be improved, and identify knowledge gaps where there is insufficient understanding of EC histogenesis. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Synovial Sarcoma of the Female Genital Tract: A Protean Mimic of Müllerian Neoplasia

Synovial sarcoma most commonly occurs in the extremities but has rarely been described in the female genital tract. In this series, we describe the clinical, morphologic, immunohistochemical, and molecular features of 7 cases of vulvovaginal synovial sarcoma (vulva, n=6; vagina, n=1). We emphasize their wide morphologic spectrum, which can overlap significantly with other more common tumors at these sites, as highlighted by 2 cases initially diagnosed as other entities (endometrioid carcinoma and malignant peripheral nerve sheath tumor). The average patient age was 41 (range: 23 to 62) years and tumor size ranged from 0.8 to 7 cm. Histologically, the tumors were biphasic (n=6) and monophasic (n=1). All cases were confirmed with fluorescence in situ hybridization or sequencing, and 5/5 cases were positive for the novel immunohistochemical markers SSX and SS18-SSX. In 3 cases with follow-up, 2 patients died of disease and 1 was alive with no evidence of disease. Previously described cases arising in the female genital tract are also reviewed. Vulvovaginal monophasic synovial sarcoma raises a broad differential diagnosis, including smooth muscle tumors, spindled carcinomas, and melanoma. Biphasic synovial sarcoma may mimic Müllerian carcinosarcoma, endometrioid carcinoma with spindled, corded, and hyalinized elements, and mesonephric-like adenocarcinoma. Awareness that synovial sarcoma can occur in the female genital tract with a wide variety of histologic appearances is critical for correctly diagnosing this rare entity. In particular, synovial sarcoma should be considered for any deeply situated "adenocarcinoma" in the vulva, with attention to subtle spindle cell differentiation.

Mesonephric-like adenocarcinoma of the ovary: A case report and a review of the literature

RATIONALE

Mesonephric-like adenocarcinoma (MLA) from ovary is a very rare tumor which derives from mesonephric duct remnant of the female genital tract. Only six cases have been reported so far in the English literature.

PATIENT CONCERNS

A 29-year-old female patient was referred to the local hospital with a 20-day history of abdominal discomfort.

DIAGNOSES

Pelvic ultrasound examination revealed a solid and cystic mass measuring 10 cm in diameter in the right adnexal area and a cystic mass measuring 5 cm in the left adnexal area. Postoperative pathology in the local hospital revealed suspected malignancy of the right ovary, and she was then transferred to our institution for definite diagnosis. The tumor mass was finally diagnosed as a primary MLA arising from the right ovary by histological and immunohistochemical examination in our institution.

INTERVENTIONS

The patient underwent laparoscopic right adnexectomy and removal of left ovarian cyst in the local institution. Then, she underwent a complete staging surgery including a total hysterectomy, left adnexectomy, pelvic plus para-aortic lymphadenectomy, and omentectomy in our hospital. In addition, she received four cycles of combination chemotherapy with carboplatin plus paclitaxel.

OUTCOMES

There is no evidence of recurrence with 13 months of follow-up till now, and we are still following-up this patient.

LESSONS

MLA is an extremely uncommon malignancy with difficult diagnosis, unclear treatment and poor prognosis. Familiarizing with the clinical features and optimal management of this rare tumor may increase awareness of the disease among clinicians and pathologists, thus avoiding the misdiagnosis and mistreatment.

Whole-proteome analysis of mesonephric-derived cancers describes new potential biomarkers

Mesonephric carcinomas (MEs) and female adnexal tumors of probable Wolffian origin (FATWO) are derived from embryologic remnants of Wolffian/mesonephric ducts. Mesonephric-like carcinomas (MLCs) show identical morphology to ME of the cervix but occur in the uterus and ovary without convincing mesonephric remnants. ME, MLC, and FATWO are challenging to diagnose due to their morphologic similarities to Müllerian/paramesonephric tumors, contributing to a lack of evidence-based and tumor-specific treatments. We performed whole-proteomic analysis on 9 ME/MLC and 56 endometrial carcinomas (ECs) to identify potential diagnostic biomarkers. Although there were no convincing differences between ME and MLC, 543 proteins showed increased expression in ME/MLC relative to EC. From these proteins, euchromatic histone lysine methyltransferase 2 (EHMT2), glutathione S-transferase Mu 3 (GSTM3), eukaryotic translation elongation factor 1 alpha 2 (EEF1A2), and glycogen synthase kinase 3 beta were identified as putative biomarkers. Immunohistochemistry was performed on these candidates and GATA3 in 14 ME/MLC, 8 FATWO, 155 EC, and normal tissues. Of the candidates, only GATA3 and EHMT2 were highly expressed in mesonephric remnants and mesonephric-derived male tissues. GATA3 had the highest sensitivity and specificity for ME/MLC versus EC (93% and 99%) but was absent in FATWO. EHMT2 was 100% sensitive for ME/MLC & FATWO but was not specific (65%). Similarly, EEF1A2 was reasonably sensitive to ME/MLC (92%) and FATWO (88%) but was the least specific (38%). GSTM3 performed intermediately (sensitivity for ME/MLC and FATWO: 83% and 38%, respectively; specificity 67%). Although GATA3 remained the best diagnostic biomarker for ME/MLC, we have identified EHMT2, EEF1A2, and GSTM3 as proteins of interest in these cancers. FATWO's cell of origin is uncertain and remains an area for future research.

Molecular profiling of mesonephric and mesonephric-like carcinomas of cervical, endometrial and ovarian origin

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KRAS mutation is a major driver in mesonephric and mesonephric-like carcinomas of cervical, endometrial or ovarian origin.

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ARID1A and PIK3CA mutations were also identified in endometrial and ovarian mesonephric-like carcinomas.

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Peripheral blood ctDNA liquid biopsy may detect mutations in recurrent and/or metastatic mesonephric carcinomas.

Mesonephric carcinoma is a rare cancer that most often arises within the cervix, and less frequently, in the ovary and endometrium. A retrospective search of our CLIA-certified and CAP-accredited reference molecular laboratory database (Foundation Medicine, Inc.) identified 20 mesonephric or mesonephric-like, cervical (n = 10), endometrial (n = 5), ovarian (n = 4) or peri-bladder (n = 1) carcinomas that had undergone comprehensive genomic profiling via next generation sequencing. Activating KRAS mutations were present in 90%, 18 of 20 cases, including G12V (n = 7), G12D (n = 6), G12A (n = 3) and G12C (n = 2). Other recurrent alterations were identified in ARID1A (25%), PIK3CA (20%), CTNNB1 (15%), TP53 (10%), MLL2 (10%) and CDKN2A (10%). One KRAS wild-type case had a GATA3 mutation as the sole alteration, while the second KRAS wild-type case had an EGFR exon 20 insertion D770_N771insSVD alteration. All tumors were negative for HPV DNA, microsatellite instability, high tumor mutational burden and homologous recombination deficiency. A circulating tumor DNA (ctDNA) liquid biopsy from peripheral blood, which was performed 6 years after original solid tumor resection in one patient with suspected lung metastasis, revealed concordance of KRAS alteration, gains of chromosomes 1q, 2, 10, 12 and 20, plus new TP53 alterations in the liquid biopsy compared to the original sample. KRAS G12 mutation is major driver of mesonephric and mesonephric-like carcinomas, with less frequent contribution by ARID1A and PIK3CA pathways in tumors of non-cervical origin. ctDNA liquid biopsy may be useful in detecting mutations in recurrent or metastatic patients, who may potentially be eligible for trials against emerging targeted therapies.

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.

Mesonephric-like adenocarcinomas of the uterine corpus: report of a case series and review of the literature indicating poor prognosis for this subtype of endometrial adenocarcinoma

PURPOSE

Endometrial mesonephric-like adenocarcinoma (ML-AC) represents a recently recognized subtype of endometrial adenocarcinoma (AC) associated with a subtle immunophenotype with a characteristic KRAS-mutation. Detailed clinico-pathologic analyses and prognostic data on ML-AC are limited.

METHODS

We report a series of four cases with histopathological, immunohistochemical, and molecular analyses. These cases as well as the data of previously published cases were reviewed for clinico-pathologic variables and clinical follow-up information.

RESULTS

Forty cases of ML-AC were identified. ML-AC represents about 1% of all endometrial carcinomas. Similar to other types of endometrial AC, vaginal bleeding was the leading presenting symptom, and the mean age was 60.0 years (range 31-91). More than a half of the patients presented with locally advanced disease (≥ FIGO stage II) at time of diagnosis, developed a recurrence or died of the disease within a mean follow-up period of 24.7 months (range 3-144.5 months). The most common site of distant disease was pulmonary involvement. Microscopically, ML-ACs present with mixed morphology and show a co-expression of so-called mesonephric and Müllerian markers, suggesting a Müllerian origin of the tumors. Immunostaining for PD-L1 was negative in all tested cases, using different antibodies against PD-L1. Retained staining for mismatch repair proteins on immunohistochemistry and a POLE-mutation suggest a copy number low phenotype within the molecular classification of endometrial carcinomas. Almost all cases showed a KRAS-mutation at codon 12 (mostly G12V).

CONCLUSION

Uterine ML-AC represents a distinct subtype of invasive endometrial AC, associated with KRAS-mutations and characteristic immunohistochemical findings. Clinically, ML-AC may show an aggressive behavior with a high rate of recurrent disease and a substantial risk for distant metastatic disease, especially to the lungs.

Mesonephric-like Carcinoma of the Endometrium: A Subset of Endometrial Carcinoma With an Aggressive Behavior

Endometrial mesonephric-like carcinomas (MLCa) are uncommon with <50 reported cases thus far. Previous studies have characterized the histologic, immunohistochemical, and molecular features of MLCa; however, there is limited information with respect to outcome. This single-institution study of 23 uterine MLCas characterizes the behavior of such a neoplasm. Uterine MLCas (2004-present) had review of histologic features, immunohistochemical results, molecular profile, and clinical information (stage, treatment, follow-up). The behavior of MLCa was compared with low-grade endometrioid carcinomas (ECas) and uterine serous carcinomas (USCs) treated at our institution from 2004 to present. All MLCas had a mixture of previously described architectural and cytologic features most notably ductal and/or tubular architecture (21/23), nuclei resembling those of papillary thyroid carcinoma (18/23), and at least focal intraluminal eosinophilic secretions (20/23). Immunoperoxidase studies facilitated diagnosis in 22 cases: CD10, 10/10; calretinin, 5/15; estrogen receptor (≥10% nuclei), 6/21; progesterone receptor, 1/15; GATA-3, 15/16; TTF-1, 11/16. Fourteen of 17 tested cases had a KRAS mutation (7 as the only alteration; 7 with additional mutations including PIK [n=5]; PTEN [n=2], CTNNB1 [n=1]).One case had mutations in PTEN, PIK, and CTNNB1 without KRAS; 2 cases had no detectable somatic mutation. Overall, 48% of patients presented with International Federation of Gynecology and Obstetrics (FIGO) stage 3 or 4 disease with the following uterine risk factors: >50% myometrial invasion, 20/23; lymphovascular space invasion, 16/23; cervical stromal invasion, 7/23. Twenty patients had adjuvant therapy (7 radiation only; 13 chemotherapy±radiation), whereas 3 patients had either unknown or declined therapy. Follow-up was known for 21 patients: 17 patients had recurrences or never achieved remission with the lung being the most common recurrence site (n=9); 7 patients died of disease. The median progression-free survival was 18.2 months for MLCa compared with 183 months for ECa and 67.1 months for USC. The median overall survival for MLCa was 70.6 months compared with 139.1 months for USC (median survival for ECa not reached). Uterine MLCa is uncommon with most tumors recognized by architectural heterogeneity, vesicular, overlapping nuclei with grooves, and eosinophilic luminal secretions. The typical immunoprofile includes low to absent expression of hormone receptors but at least focal expression of GATA-3 and/or TTF-1. Most tested cases had a KRAS mutation although genetic mutations typically associated with ECa are not uncommon. Compared with more commonly encountered types of ECa, MLCa is more aggressive with a tendency towards earlier and distant recurrence.

Coexistence of endometrial mesonephric-like adenocarcinoma and endometrioid carcinoma suggests a Müllerian duct lineage: a case report

Background

Endometrial mesonephric-like adenocarcinomas exhibit classical histologic features of mesonephric carcinoma; however, it remains unclear whether these tumors represent mesonephric (Wolffian) carcinoma or endometrioid (Müllerian) carcinomas that closely mimic mesonephric carcinoma.

Case presentation

A 32-year-old Japanese primigravida presented with atypical vaginal bleeding. An endometrial biopsy suggested low-grade endometrioid carcinoma, and she was administered medroxyprogesterone acetate. Her tumor recurred 6 years later, and she underwent hysterectomy, salpingo-oophorectomy, and omentectomy, at which point she was diagnosed with mesonephric-like adenocarcinoma of the uterine endometrium. Retrospective pathological review of the initial biopsy confirmed coexisting low-grade endometrioid carcinoma and mesonephric-like adenocarcinoma of the uterine endometrium. On immunohistochemistry, the endometrioid carcinoma component was diffuse positive for estrogen and progesterone receptors but negative for thyroid transcription factor 1. However, the mesonephric-like adenocarcinoma component exhibited a mixture of estrogen receptor- and thyroid transcription factor 1-positive cells within the same glands.

Conclusions

We encountered a patient with coexisting endometrial mesonephric-like adenocarcinoma and low-grade endometrioid carcinoma, which was treated using medroxyprogesterone acetate therapy, resulting in recurrence of mesonephric-like adenocarcinoma alone. These clinicopathological findings support the prevailing notions that mesonephric-like adenocarcinoma is a Müllerian adenocarcinoma exhibiting mesonephric differentiation.