Very well differentiated adenocarcinoma of the colon: a case report.

A 47-year-old woman with chronic colitis was found to have a sessile tumor at the hepatic flexure of the colon. An endoscopic biopsy revealed no aytpia, but surgery was performed since, in view of the tumor's size, malignancy could not be ruled out. A tumor measuring 3 x 2 x 1.5 cm was found in the resected specimen. The tumor exhibited quite unusual histologic features, showing invasive, moderately atypical glands forming mucin-filled cysts, very similar to those seen in colitis cystica profunda, under pseudopolypoid mucosa covered by non-atypical glandular epithelial cells. The extension of glandular elements into the pericolonic fatty tissue, and the intermingling of anaplastic microglands led to a final diagnosis of adenocarcinoma. In a case such as this, it is very difficult to evaluate cancerous tissue by endoscopic biopsy, even with an amount of tissue adequate for histologic examination.