A case of collision tumor of cecal adenocarcinoma and appendiceal mucinous cystadenocarcinoma in a patient with ulcerative colitis

Abstract

We report a case of collision tumor with cecal adenocarcinoma and appendiceal mucinous cystadenocarcinoma associated with ulcerative colitis. A 62-year-old man treated with prednine and salazopyrin since suffering ulcerative colitis at 27 years of age stopped taking his medicine after entering remission in 1998. He then suffered anemia in November 2004. Colonoscopy showed findings compatible with mild ulcerative colitis, and detected a type-2 tumor in the cecum that proved in a biopsy to be well differentiated adenocarcinoma. He underwent right hemicolectomy in February 2005. The postoperative macroscopic specimen showed another appendiceal tumor filled with mucin inside next to the cecal tumor, i.e., two different types of carcinoma, well-differentiated adenocarcinoma and mucinous cystadenocarcinoma, colliding at a clear boundary without intermingling. These findings satisfy rigorous criteria for collision tumor. Primary colorectal collision tumor is rare, and this case may be the first reported with both of these components. © 2007 The Japanese Society of Gastroenterological Surgery.