Diagnostic and pathogenetic implications of colorectal carcinomas with multidirectional differentiation: a report of 4 cases.

Multidirectional differentiation in colorectal carcinomas is a rare phenomenon. Four cases are reported herein, and their clinical and pathologic characteristics are discussed. Two men and 2 women between the ages of 56 and 76 years who presented with abdominal symptoms are included in this report. Two tumors were located in the right colon, one in the splenic flexure, and one in the descending colon. Distant metastases were evident at presentation in 3 of 4 cases. Histologically, two tumors exhibited neuroendocrine and glandular differentiation; the third tumor was an adenocarcinoma with a sarcomatous component and the fourth tumor showed 3 lines of differentiation (glandular, squamous, and sarcomatoid). In all tumors evaluated, areas of adenocarcinomas were positive for low-molecular weight cytokeratin (CAM 5.2) and mucicarmine, but negative for high-molecular weight cytokeratin (AE3). The squamous cell component was AE3 positive and CAM 5.2 negative. The neuroendocrine component was highlighted by neuroendocrine markers and the sarcomatoid component revealed smooth muscle differentiation. All tumors (except one mucinous tumor) were negative for cytokeratin-20 staining. One patient was on supportive care for terminal metastatic carcinoma, and 2 patients were being treated with adjuvant chemotherapy at the time of this report. Colon carcinoma with multidirectional differentiation is a rare event and may originate from stem cells within the gastrointestinal mucosa, and/or represent the convergence of multiple tumors arising at the same site. This type of tumor should be considered in the differential diagnosis of a bowel biopsy with multiple histopathologic variants.