A Rare Case of Undifferentiated Carcinoma of the Colon Directly Invading the Duodenum

Abstract

Colorectal cancers often invade adjacent organs; however, direct duodenal invasion is rare. Adenocarcinoma is the most common type of colorectal cancer, but an undifferentiated carcinoma type is unusual. Herein, we present a case of undifferentiated carcinoma of the colon that directly invaded the duodenum and metastasized to distant lymph nodes. An 85-year-old female patient was admitted with a 7-cm-sized colonic mass invading the duodenum, detected by computed tomography. Positron emission tomography revealed fluorodeoxyglucose uptake in the colon, duodenum, and aortocaval lymph nodes. A large encircling mass in the ascending colon and an ulcerated mass in the duodenum were revealed by colonoscopy and esophagogastroduodenoscopy, respectively. Pathologic examinations of the colon and the duodenum revealed nonglandular, diffusely infiltrating atypical round cells, confirming undifferentiated carcinoma of the colon. The histologic type of this tumor was distinguished using immunohistochemical (IHC) markers. Finally, microscopic characteristics and IHC markers aided in identifying the histologic type of colorectal cancer.