Collision Tumor of the Large Bowel in the Context of Advanced Pregnancy and Ulcerative Colitis

A woman aged 33 years, during week 30 of pregnancy, presented with metastatic, high-grade neuroendocrine cancer. Investigation revealed a collision-type primary tumor of the large bowel, containing adenocarcinoma and neuroendocrine elements. Platinum-based chemotherapy resulted in a divergent pathologic response as assessed after colectomy. The diagnosis and classification of mixed endocrine-exocrine tumors of the colon are discussed, along with treatment considerations.