Carcinoma of müllerian origin presenting as colorectal cancer: A clinicopathologic study of 13 Cases

Carcinomas of müllerian origin involving colorectum in women with no concurrent or history of gynecologic malignancies are diagnostically challenging, and its histogenetic origin is uncertain. We reviewed 13 cases of carcinoma of müllerian origin with clinical presentation mimicking primary colorectal carcinoma. The patients' average age was 63.9 years. All except 2 patients presented with mass lesions in rectosigmoid colon or rectovaginal septum. The major presenting symptoms were rectal bleeding (4/13), rectosigmoid mass (6/13), vaginal mass (1/13), and abdominal pain or constipation (2/13). The average size of tumor was 4.2 cm (range, 2.4-15.0 cm). Among the 10 patients who underwent preoperative biopsy, 5 were diagnosed to have moderately and poorly differentiated colorectal carcinoma. All tumors were surgically resected with final diagnoses of moderately differentiated endometrioid carcinoma in 6 cases, mixed serous and endometrioid carcinoma in 4 cases, malignant mixed müllerian tumor in 2 cases, and undifferentiated carcinoma in 1 case. In 9 of 13 cases, foci of endometriosis were identified adjacent to or within the tumor. One case had endosalpingiosis. Immunohistochemical stains showed, after positive results, the following: cytokeratin 7 (CK7; 13/13), estrogen receptor (13/13), progesterone receptor (10/13), cytokeratin 20 (CK20; 0/13), and CDX-2 (0/13). In conclusion, carcinoma of müllerian origin often presents as bulky mass in rectosigmoid or rectovaginal septum clinically mimicking primary colorectal cancer. Endometriosis might be an important etiologic factor. Familiarities of this unusual clinicopathologic entity, careful morphologic evaluation, and immunohistochemical stain with a panel of markers (CK7, CK20, estrogen receptor, progesterone receptor, CDX-2) will be helpful for the correct diagnosis.