Answer: Concurrent endometrioid carcinoma of the endometrium and adenocarcinoma of colorectum

Histology: Specimen from endometrial curettage revealed compact/cribriform atypical endometrial glands in a desmoplastic stroma, typical for well differentiated endometrioid carcinoma of the endometrium (FIGO grade 1). The sections from transvaginal biopsy show variable size mucinous glandular epithelium with moderate to marked cytological atypia, suggestive of moderately differentiated colorectal adenocarcinoma.

Discussion: This young woman has a significant family history for early-onset colon cancer (her father and a sister). She was diagnosed to have concurrent endometrial and colorectal carcinomas. This has been confirmed by immunohistochemical stains. The tumors with endometrioid morphology are positive for CK7, ER, PR and CA125, but negative for CK20. The tumors with colorectal carcinoma morphology are only positive for CK20, and negative for all other markers. In view of patient’s young age, significant family history and concurrent endometrial and colorectal carcinomas, we speculate that this patient may have hereditary non-polyposis colon cancer (HNPCC) syndrome. HNPCC syndrome is characterized by germline mutations in DNA mismatch repair genes and by microsatellite instability in tumors. In fact, endometrial carcinoma is the second most common cancer next to colon cancer occurring in female HNPCC patients. It is also interesting to notice that her endometrial carcinoma lacks expression of pTEN (a tumor suppressor, often inactivated in endometrioid carcinomas), while pTEN immunoreactivity was seen in her colorectal carcinoma.