Serous endometrial carcinoma metastatic to the sigmoid colon masquerading as a primary colon cancer detected by bowel obstruction.

BACKGROUND

The majority of colorectal malignancies are primary tumors. Secondary tumors are rare, and colorectal metastasis from endometrial carcinoma is exceptionally uncommon. We report a case of serous endometrial carcinoma that metastasized to the sigmoid colon, initially presenting as a primary colon carcinoma due to bowel obstruction.

CASE PRESENTATION

A 79-year-old woman presented with abdominal distention and constipation. Five years earlier, she had undergone an open total hysterectomy with bilateral salpingo-oophorectomy for endometrial serous carcinoma. A colonoscopy revealed stenosis encircling the entire sigmoid colon. Abdominal computed tomography demonstrated irregular wall thickening in the sigmoid colon with enhanced regional lymph node enlargement and upstream bowel dilatation. Peritoneal dissemination in the pelvis was also noted. To relieve the obstruction, two self-expanding metal stents were inserted. Subsequently, due to the presumed diagnosis of sigmoid colon carcinoma with peritoneal dissemination, an open left hemicolectomy with resection of the peritoneal dissemination was performed. Histopathological examination identified the colon tumor and peritoneal dissemination as metastatic serous endometrial carcinoma. Immunohistochemical studies showed the tumor cells were negative for CK7, CK20, and CDX2. No chemotherapy was administered, and 6 months post-operation, no recurrence was observed.

CONCLUSIONS

Metastasis of endometrial carcinoma to the colon is extremely rare. Diagnosing a colon tumor as a metastasis from endometrial carcinoma is challenging during preoperative examinations. Therefore, in patients with a history of endometrial carcinoma, the possibility that the primary site might be the uterus should be considered.