Endometrial carcinoma with yolk sac tumor-like differentiation and elevated serum β-hCG: a case report and literature review

Yolk Sac Differentiation in Endometrial Carcinoma: Incidence and Clinicopathologic Features of Somatically Derived Yolk Sac Tumors Versus Carcinomas With Nonspecific Immunoexpression of Yolk Sac Markers

Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/- morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

Yolk sac tumor of postpubertal-type does not exhibit immunohistochemical loss of SMARCB1/INI1 and SMARCA4/BRG1…but choriocarcinoma?

The recently described SWI/SNF complex-deficient sinonasal carcinoma (SMARCB1 & SMARCA4) may exhibit a yolk sac-like morphology. Tumors with similar features (yolk sac-like histology combined with the immunohistochemical loss of SMARCB1/INI1 and/or SMARCA4/BRG1) have also been described in other sites, such as the female genital tract. In this study, we immunohistochemically assessed SMARCB1/INI1 and SMARCA4/BRG1 expression to evaluate if these proteins could be involved in the pathogenesis of testicular yolk sac tumors of postpubertal type (YSTpt). Specifically, we analyzed a retrospective case series comprising pure YSTpt and mixed germ cell tumors of the testis (GCTT) with YSTpt components. In the present study, no testicular YSTpt showed loss of SMARCB1/INI1 (0/24, 0%) or SMARCA4/BRG1 (0/24, 0%). However, testicular choriocarcinoma (CHC) and isolated syncytiotrophoblast cells (iSTCs) demonstrated abnormal staining patterns for SMARCA4/BRG1 [CHC: 4/4 (100%); iSTCs: 12/12 (100%), respectively], including focal or diffuse loss of expression in a subset of cases. The results of our study suggest that functional loss of SMARCA4/BRG1 represents a recurrent event that may be relevant for the pathogenesis of a subset of testicular CHC.

Post-pubertal ovarian yolk sac tumor with unusual follicular growth pattern, simulating struma ovarii

Yolk sac tumors (YST), formerly known as endodermal sinus tumors, are uncommon ovarian neoplasms. They are most common in the second and third decades of life and are rare in women older than 39 years of age. YST exhibit various histologic patterns. Microfollicular pattern resembling thyroid tissue has not been reported. We introduce here a case of yolk sac tumor in a 39 y/o female, presented with pelvic masses and high level of serum Alpha-fetoprotein (Alpha Fetoprotein) (> 1000 IU/ml). The patient underwent left salpingo-oophorectomy. On microscopic study, morphologic findings demonstrated a neoplasm composed of follicular structures with eosinophilic intraluminal content, resembling struma ovarii on low-power field. On Immunohistochemistry study, the tumor cells were positive for Alpha-fetoprotein and Glypican-3. Epithelial Membrane Antigen (EMA), Thyroglobin (TG), Thyroid transcription Factor-1 (TTF1) and sex-cord stromal markers were negative. This case introduces a new histomorphologic pattern of yolk sac tumor in a middle-aged woman. It is important to know that yolk sac tumor can exhibit various histological appearances. Regarding patient’s clinical and laboratory findings, this differential diagnosis should be kept in mind for proper diagnosis of similar cases.

Yolk sac tumor of the uterus in a 2-year-old girl: A case report and literature review

BACKGROUND

Extragonadal yolk sac tumors (YSTs) occurring in the uterus are extremely rare. To report a uterine YST case in a prepubertal girl and review literature on uterine YST to outline clinical management in diagnosis and treatment.

CASE

We present a case of a 2-year-old girl who presented with vaginal bleeding and a pelvic mass. The diagnosis of YST was confirmed via biopsy. After four cycles of neoadjuvant chemotherapy combined with cisplatin, etoposide, and bleomycin (PEB), vaginoscopic examination and laparoscopy revealed a uterine YST without metastasis. The patient was treated with laparoscopic hysterectomy and two cycles of PEB postoperatively. During the 18 months of follow-up, the patient remained disease-free.

SUMMARY AND CONCLUSION

Primary uterine YST is extremely rare and no treatment guidelines have been established to date. Surgery combined with PEB chemotherapy is considered effective for uterine YST.

Pure primary yolk sac tumor of the endometrium tends to occur at a younger age: A case report and literature analysis

We present a case of primary yolk sac tumor of the endometrium. This rare tumor occurred in a 43-year-old woman with a pure primary yolk sac tumor. The tumor resembled yolk sac tumor morphology of the ovary. Tumor cells expressed SALL4, AFP, GPC-3, and AE1/AE3 and were focal positive for PAX8. EMA, ER, and PR, among others, were negative. We further analyzed 29 reported cases of this rare tumor in the literature. In total, 17 of 30 patients (57%) had pure endometrial yolk sac tumor, and 13 (43%) had a concomitant somatic neoplasm (endometrial adenocarcinoma was the most common). Although the average age was 52 years (range: 24–87 years), patients with pure yolk sac tumor were younger than those with concomitant somatic tumors, with a mean age of 44.41 years (24–68 years) versus 61.92 years (28–87 years), P = 0.008. Patients with endometrial yolk sac tumor combined with somatic tumor tend to have a slightly higher stage and a poor prognosis.

Case Report: Extragonadal Yolk Sac Tumors Originating From the Endometrium and the Broad Ligament: A Case Series and Literature Review

Yolk sac tumors (YSTs) of the endometrium and the broad ligament are very rare, with only 29 cases and one case of each other reported before in the English literature. Due to lack of standard guidelines, the treatment strategies of these diseases are controversial. Here, we share two cases of YSTs originating from the endometrium and the broad ligament respectively and review related literature. A 35-year-old woman was diagnosed with endometrial YST in our center and underwent surgery followed by chemotherapy with BEP (bleomycin, cisplatin and etoposide) regimen for six courses. After follow-up for 21 months, there is still no evidence of relapse. Another 36-year-old woman was admitted to our department with YST of the broad ligament. She was treated with surgery followed by chemotherapy with BEP regimen and was lost to follow-up after completing therapy. The case of endometrial YST we shared was similar to cases reported before, while the case with YST of the broad ligament we shared was the second case reported worldwide. Both of these two cases were treated with surgery combined with chemotherapy with BEP regimen.

Extragonadal Yolk Sac Tumor Limited to the Myometrium: Report of a Case With Potential Fertility Preservation and Molecular Analysis Suggesting Germ Cell Origin

Extragonadal pelvic yolk sac tumor (YST) in postpubertal female patients is a rare malignant neoplasm with potentially 2 distinct histogenetic pathways, and no clear treatment algorithm, especially in young patients desiring future fertility. Here we report a case of extragonadal YST arising within the myometrium in a 30-yr-old nulligravid woman. The patient presented with heavy and irregular bleeding, and imaging studies showed an 8.2 cm uterine mass, most consistent with a degenerating uterine leiomyoma. The patient underwent abdominal myomectomy, and intraoperative frozen section evaluation revealed a high-grade malignancy. Because of the patient's strong desire for future fertility, a conservative wedge resection of the surrounding myometrium and surgical staging with uterine closure and retention of the ovaries were performed. On permanent sections the tumor showed an admixture of glandular, reticular, solid and papillary architectural patterns, moderate to marked nuclear atypia and clear cytoplasm with focal eosinophilic hyaline globules. Immunohistochemical stains were diffusely positive for SALL4, AFP, glypican3, and focally positive for CK20, and negative for EMA, and CK7, confirming the diagnosis of extragonadal YST. The endometrium displayed normal secretory phase morphology without involvement by YST, and the myometrial resection margins were negative. Short tandem repeat genotyping analysis of the tumor revealed allelic gains at 7 loci (involving chromosomes 2, 3, 4, 5, 8, 13, and 15) and allelic loss at one locus assessed on chromosome 11, while next-generation sequencing results showed no mutations in 155 genes tested, suggesting germ cell origin. The patient underwent 4 cycles of adjuvant chemotherapy with bleomycin, etoposide, and cisplatin, and she had 1 cycle of successful oocyte cryopreservation 6 months after completing chemotherapy. The clinical follow-up at 12 mo shows no evidence of disease.

Yolk sac tumor of endometrium: A case report and literature review

OBJECTIVE

To report a rare case of endometrial yolk sac tumor (YST) and review published cases of YST of the endometrium.

CASE REPORT

A 68-year-old female presented with intermittent vaginal spotting for nine months. An endometrial biopsy showed adenocarcinoma. Complete surgical staging operation was performed and the final pathology revealed stage II endometrial yolk sac tumor. The post-operative α-fetoprotein (AFP) level was 133.4 ng/mL. Post-operative adjuvant chemotherapy with bleomycin, etoposide, and cisplatin (BEP) regimen was prescribed for 6 cycles. AFP levels were normal before the fourth cycle of chemotherapy. She is disease free 6 months after completion of therapy.

CONCLUSION

Primary YSTs arising in the endometrium is an extremely rare disease especially in postmenopausal women. Complete surgical staging operation with adjuvant chemotherapy will lead to good outcome in this disease.

Mixed Germ Cell Tumor of the Endometrium: A Case Report and Literature Review

Germ cell tumors (GCTs) localized extragonadally are rare, with only 14 reported cases of a yolk sac tumor in the endometrium. Here we report a case of mixed endometrium GCTs in a 65-year-old postmenopausal woman with abnormal vaginal bleeding. An ultrasound examination showed an oval-shaped mass in the patient’s uterine cavity. Biochemical examination revealed elevated serum α-fetoprotein (AFP) at 359 ng/mL, whereas the tumor markers CA-125, CA-199, and CEA were all within normal range. Total hysterectomy and bilateral salpingo-oophorectomy were performed;. a histological examination revealed that the malignant components contained a yolk sac tumor, embryonal carcinoma, and focal immature teratoma. Immunohistochemical staining showed that AFPs were diffusively distributed in both the yolk sac tumor and embryonal carcinoma. The stem cell marker OCT3/4 was positive in the embryonal carcinoma component and that the pan-cytokeratin AE1/AE3 staining was positive in glandular areas. GFAPs (Glial Fibrillary Acidic Proteins) were positive in neuroectodermal tubules; the Ki-67 protein was positive in 90% of the tumor cells, whereas CD117 and placental alkaline phosphatase (PLAP) were negative. The cumulative evidence indicated mixed GCTs of endometrium as the final histopathological diagnosis. The patient received three courses of adjunct chemotherapy that provided good therapeutic efficacy as evidenced by the decreased serum AFP level. Our report on this rare case of mixed GCTs of the endometrium, supported by associated histological patterns and immunophenotypes and successful adjunct chemotherapy after surgery, could provide insight on future treatment of this rare but lethal disease.

Endometrial tumors with yolk sac tumor-like morphologic patterns or immunophenotypes: an expanded appraisal

Uterine yolk sac tumors have gained increased recognition in recent years. The current study is a multi-faceted examination of yolk sac tumor-like phenotypes in endometrial tumors, based on an analysis of 3 groups of uterine tumors: Group 1: 9 endometrial tumors that had been classified as yolk sac tumor, or as having a yolk sac tumor component, were assessed with a 35-marker immunohistochemical panel, with the goal of defining their immunophenotypic spectrum; Group 2, comprised of 70 endometrial carcinomas of various histotypes, were analyzed for their expression of SALL4, Glypican-3, and AFP, to assess the specificity of these markers for yolk sac tumors relative to endometrial carcinomas; Group 3, comprised of 626 archived cases of endometrial carcinoma/carcinosarcoma, reviewed to define the frequency of yolk sac tumor-like morphology therein. Yolk sac tumor areas in the Group 1 cases were consistently immunoreactive for SALL4 and Glypican-3; variably positive for AFP (89%), Villin (89%), PLAP (78%), 34βE12 (67%), CAM 5.2 (62.5%), EMA (56%), CD117 (50%), p16 (50%), CDX2 (44%), p53 (44% aberrant), MOC31 (37.5%), CK7 (33%), GATA3 (33%), CK5 (25%), and PAX8 (11%); and were negative for CD30, Napsin A, OCT4, estrogen, androgen, and progesterone receptors. 29 (41%) of the 70 group-2 cases expressed at least one of the 3 markers, and 96% of the positive cases was a high-grade histotype. Glypican-3, SALL4, and AFP were positive in 30, 20, and 2.8% of group-2 cases respectively; however, co-expression of any 2, or all 3 markers was uncommon (<9 and 1.4% of cases respectively). Potential yolk sac tumor-like morphology was identified in 5 (0.8%) of 626 group-3 cases, and three were ultimately deemed to be true yolk sac tumor phenotypes based on their morphologic and immunophenotypic similarity to the group 1 cases. These findings highlight the broad immunophenotypic spectrum of uterine yolk sac tumors, the potential pitfalls associated with using immunophenotypes alone to define yolk sac tumor differentiation in endometrial carcinoma, and the utility and limitations of morphologic assessment to identify yolk sac tumors at this site.

Primary yolk sac tumor of the endometrium: a case report and review of the literatures

PURPOSE

Yolk sac tumor (YST) is a malignant tumor derived from germ cells and usually occurs in the gonads. Extra-gonadal YST is most commonly seen in the vagina of children, but rarely in the cervix, vulva and endometrium. Primary YST of endometrium was extremely rare, standard treatment was still controversial and no guideline was established so far. The aim of the present study was to provide a comprehensive understanding and systematic thought for the management of primary YST of endometrium.

METHODS

A systematic research of the literature was conducted in Scopus, PubMed database and Cochrane Library, including case reports and case series. We summarized clinical characteristics, treatments and prognosis of all collected cases. We collected data regarding patients, serum AFP level, initial symptoms, surgical information, postoperative chemotherapy and radiotherapy. A new case was also discussed.

RESULTS

We found only 26 cases have been reported previously. We reported a new case of primary endometrial YST in a 27-year-old woman, and in this case, we creatively performed bilaterally ovarian preservation and used DC (docetaxel and carboplatin) regimen of postoperative chemotherapy, we achieved a relatively good prognosis during the follow-up period of 14 months.

CONCLUSION

Primary YST of endometrium, kind of highly malignant germ cell tumors, was extremely rare, of which initial symptom is usually abnormal vaginal bleeding. Standard treatment was still controversial and no guideline was established so far. Surgery combining with postoperative chemotherapy was considered effective for treatment of primary endometrial YST. Decision on whether to preserve ovaries in young patient with early stage needs careful consideration, comprehensive preoperative assessment and full communication. Intraoperative biopsy and strict postoperative follow-up are recommended. However, standard chemotherapy regimen and feasibility of postoperative radiotherapy remains to be discussed.

Primary yolk sac tumor originating from the endometrium: A case report and literature review

RATIONALE

Yolk sac tumors (YSTs) are malignant germ cell tumors that secrete alpha-fetoprotein (AFP). These tumors commonly develop in infants, young children, and young women and often originate in the gonads. Primary endometrial YST is a very rare malignancy, and a primary endometrial YST in the absence of abnormal AFP levels is even rarer.

PATIENT CONCERNS

A 38-year-old woman presented with the chief complaint of prolonged menstruation and increased menstrual bleeding with a duration of more than 2 months.

DIAGNOSES

Postoperative pathology confirmed a diagnosis of endometrial YST with metastasis to the greater omentum (stage IVB).

INTERVENTIONS

The patient underwent a laparoscopic extrafascial hysterectomy, bilateral adnexectomy, pelvic lymphadenectomy, abdominal para-aortic lymphadenectomy, omentectomy, and appendectomy. Additionally, she received 6 courses of multidrug chemotherapy (bleomycin, etoposide, and cisplatin; BEP).

OUTCOMES

After completing chemotherapy, the patient underwent regular follow-up examinations. No recurrence was noted during a 24-month follow-up period.

LESSONS

YST is mainly treated using surgery and chemotherapy, which may spare endocrine functions in young patients. The BEP regimen appears to be an effective postoperative chemotherapy regimen for patients with endometrial YST.

Extensive trophoblastic differentiation in case of an endometrial carcinoma

Trophoblastic differentiation of endometrial carcinoma is extremely rare, till date 18 cases reports are there in the literature. A 68-year-old postmenopausal female presented with abnormal vaginal bleeding. Histopathologically, there were areas of serous carcinoma with trophoblastic differentiation (~90%). On immunohistochemistry, the trophoblastic component was positive for β-human chorionic gonadotropin (hCG), HPL and EMA. IHC confirmed the diagnosis of serous carcinoma with trophoblastic differentiation. The clinicopathological features of 18 previously reported cases of trophoblastic differentiation in the uterine tumor were analyzed in addition to the present case.

Endometrial Carcinoma With Trophoblastic Components: Clinicopathologic Analysis of a Rare Entity

Somatic endometrial carcinomas with trophoblastic components have only rarely been described. To better characterize this distinctive combination of histotypes, we report herein 4 new cases, representing the largest cohort reported thus far, and review previously reported cases. The 4 new patients ranged in age from 61 to 77 yr (mean, 68 yr). The first patient had a grade 2 endometrioid carcinoma, surgical International Federation of Gynecology and Obstetrics stage IA, that recurred 5 months later at the vaginal apex with purely choriocarcinoma elements, suggestive of unsampled trophoblastic areas in the uterus. The 3 other patients were all International Federation of Gynecology and Obstetrics stage III, and included 2 cases of dedifferentiated endometrial carcinoma with 40% and 20% choriocarcinoma components, and 1 case of grade 1 endometrioid carcinoma with a 40% choriocarcinoma component. Postoperative serum β-human chorionic gonadotropin was elevated in all patients. All received adjuvant combination chemotherapy, but all were dead of disease with distant metastases at an average of 11.75 mo (range, 7-16 mo) after primary staging. Data from our cases were combined with those from 24 cases that had previously been reported in the literature between 1972 and 2016. Analysis of this combined data indicates that endometrial carcinoma with trophoblastic component is a rare neoplasm that occurs primarily in postmenopausal patients. The trophoblastic component is most commonly a choriocarcinoma and the somatic component is most commonly an endometrioid carcinoma or an adenocarcinoma/carcinoma reported without further specification; the somatic component may be a diverse array of histotypes or histotype admixtures. Serum and/or urine β-human chorionic gonadotropin is elevated in almost all patients, and fluctuations of β-human chorionic gonadotropin generally correlated with tumor relapses or recurrences. The stage distribution and patient outcomes in the current and previously reported patients suggests that trophoblastic differentiation usually, but not invariably denotes clinical aggressiveness.

Hormone producing gynecological tumors: pathologic entities and clinical significance

INTRODUCTION

Due to their derivation from the cell types involved in gynecologic hormonal networks, many gynecologic tumors may produce hormones. In a normal physiological setting, these hormones are essential for regulating the biology and function of gynecological organs, the ovary and uterus in particular. Overproduction of hormones by the tumor may lead to abnormal clinical manifestations of the patients and spillage of excess hormonal products into the blood. Abnormal elevation of serum hormones may be considered as biomarkers that are important to pathologists and clinicians in making precise tumor diagnoses and likely useful in monitoring the tumor burden/recurrence to guide patient treatment options. This review will discuss gynecologic neoplasms that produce hormonal biomarkers and assess their relevance to pathological diagnosis, evaluation for therapeutic response and monitoring disease progression.

AREAS COVERED

Studies involving hormonal production by a gynecologic tumor were candidates for inclusion in this review.

EXPERT COMMENTARY

Serum hormonal biomarkers have clinical utility both in the diagnosis of gynecologic neoplasms and clinical monitoring of treatment efficacy and recurrence.

Primary Endometrial Yolk Sac Tumor With Endodermal-Intestinal Differentiation Masquerading as Metastatic Colorectal Adenocarcinoma

Yolk sac tumors (YSTs) with a somatic glandular pattern can be difficult to recognize histologically because they reproduce developing intestinal, hepatic, or lung tissue and can express markers such as CDX2 and TTF1. We report an unusual case of a primary endometrial YST showing florid endodermal-intestinal differentiation in a 63-yr-old woman with a history of colorectal adenocarcinoma. Histologically, the tumor exhibited a glandular and papillary architecture and showed widespread immunoreactivity for CDX2 and focal staining for CK20 and CEA, mimicking metastatic colorectal carcinoma on biopsy. The presence of subnuclear cytoplasmic clearing and positive staining for germ cell markers, however, pointed toward a diagnosis of primary endometrial YST, and this was supported by the radiologic and the subsequent pathologic finding of a primary endometrial-based lesion. YSTs in this age group usually arise in association with somatic tumors and in this case a small focus of coexistent endometrioid adenocarcinoma was identified within the uterus. Despite surgery and adjuvant chemotherapy, the patient showed disease progression with liver and lung metastases 6 mo postoperatively.

Yolk Sac Tumor in Extragonadal Pelvic Sites: Still a Diagnostic Challenge

We present the clinicopathologic features of 15 cases of extragonadal yolk sac tumor (EGYST) detected in female patients and reviewed at our institution from 1988 to 2016. We recorded: patient age, clinical presentation, tumor location, FIGO stage (where applicable), histologic patterns including presence/absence of Schiller-Duval bodies, other germ cell or somatic components, immunoperoxidase results, treatment, and outcome. Patients' ages ranged from 17 to 87 (median, 62) years and presentation included: abnormal uterine bleeding, 12; hematuria, 1; labial mass, 1; abdominal pain, 1. Primary sites were as follows: uterus (11), vagina (1), vulva (1), bladder (1), and peritoneum (1). Seven patients presented at FIGO stage III or IV. The following histologic patterns were observed: microcystic/reticular (7), glandular (8), solid (8), papillary (5), and hepatoid (1). An admixture of histologic patterns was present in 10 cases. Schiller-Duval bodies were seen in only 3 (23%) cases. Eight cases (46%), all uterine primaries, had associated somatic components, and 2 (15%) had a second germ cell component. In 13/14 (93%) cases, the yolk sac tumor component was either missed or misclassified as adenocarcinoma. Immunoperoxidase studies facilitated the diagnosis in all cases as follows: SALL4, 12/12; CDX2, 10/12; α fetoprotein, 7/14; glypican-3, 9/10; cytokeratin 20, 5/9 (rare cells); cytokeratin 7, 3/12 (nondiffuse); PAX8, 2/9 (variable expression). All patients received chemotherapy and all except 1 underwent surgical resection. Follow-up from 5 to 86 months was available for 13 patients: 5 died of disease, 6 are alive with disease, and 2 have no evidence of disease. EGYST arising in the female pelvis of peri/postmenopausal patients may be associated with a somatic component and represent either somatically derived YST or YST differentiation within a somatic carcinoma. EGYST in younger patients is likely a true germ cell neoplasm, and may respond to germ cell appropriate chemotherapy. The benefit of germ cell appropriate chemotherapy in somatically derived EGYST is less clear. Awareness that the presence of glandular or microcystic patterns may lead to under-recognition or misdiagnosis of EGYST in combination with immunomarkers for germ cell and yolk sac differentiation will facilitate the diagnosis.

Intestinal differentiated mucinous adenocarcinoma of the endometrium with sporadic MSI high status: a case report

Background

Intestinal differentiation of primary mucinous adenocarcinoma of the uterine corpus is exceedingly rare in comparison to the approximately 25% rate in endocervical and ovarian mucinous carcinoma. Additionally, little is known about the related genetic and epigenetic alterations, even though large-scale molecular characterisation of the different types of endometrial cancer took place in the TCGA project along the entities defined by the recent WHO classification.

Case presentation

We present a 62-year-old patient harbouring a primary mucinous carcinoma of the uterine corpus with a morphological resemblance to mucinous colorectal adenocarcinoma. The intestinal differentiation was substantiated by CDX2 and CK20 positivity in the absence of PAX8, p16, WT1, p53, ER, PgR, AFP, SALL4 and Glypican3. A high MSI status with MLH1 hypermethylation was revealed by molecular testing.

Conclusion

Intestinal differentiation of mucinous adenocarcinoma of the endometrium is a unique observation. Besides morphology, it obviously can share molecular features of sporadic MSI colorectal cancers. It can be speculated that either CDX2 positive morula formation or intestinal metaplasia of the endometrium as rare conditions might be the origin of carcinogenesis for this type II endometrial cancer. Both conditions were not detectable in this case. Of note, categorising endometrial cancers in genetic subgroups like MSI high cancers alone might lead to the integration of likewise morphologically different tumours like the case presented here with intestinal differentiation. Hence, careful genotype-phenotype correlations are warranted for studies of mucinous adenocarcinoma of the endometrium.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-017-0629-0) contains supplementary material, which is available to authorized users.