Delayed metastatic endometrial carcinoma mimicking primary colon adenocarcinoma: A surprise histopathological finding

KEY CLINICAL MESSAGE: Colorectal cancer is the third most common malignancy worldwide, with an increasing incidence. Colonic metastasis is a rare occurrence; thus, misdiagnosis is common. Immunohistochemistry facilitates accurate diagnosis and subsequent management. ABSTRACT: Most cancers in the colon are primary colorectal cancers, however metastasis from another primary is possible, albeit rare. Endometrial cancer metastasis to the colon is a rare occurrence and is only described in a handful of cases. We describe a rare case of metastatic endometrial cancer in the colon presenting 5 years post radical hysterectomy and adjuvant radiotherapy in a 62-year-old female. She presented with a 1-week history of right upper quadrant pain, with no other associated symptoms. She was presumed to have a primary colorectal cancer based on her colonoscopy and CT findings; later proven otherwise by immunohistochemistry (IHC). Endometrial cancer metastasis to the colon is rare, thus misdiagnosis can easily occur. Currently, there are 6 similar cases reported in the literature, all occurring in the absence of colorectal endometriosis. This case illustrates the relative importance of considering colon as a potential site for metastasis of endometrial cancer and the utility of IHC in aiding diagnosis and guiding further management.