Medullary Carcinoma of the Colon: A Case Report

Abstract

Colorectal cancer (CRC) is a significant global health burden. Medullary carcinoma (MC) of the colon is a rare histological subtype, accounting for less than 3% of CRCs and often associated with hereditary nonpolyposis colorectal cancer (HNPCC). It is characterized histologically by sheets of poorly differentiated tumor cells with lymphocytic infiltration and loss of MLH1 expression. We report a case of a diabetic male in his 40s presenting with right-sided abdominal pain and features of intestinal obstruction. Imaging revealed right colon thickening, and the patient underwent emergency right hemicolectomy. Histopathology confirmed medullary carcinoma (pT2N0) with MLH1 loss. One year later, recurrence was detected, and the patient underwent abdominal colectomy with ileorectal anastomosis followed by adjuvant chemotherapy. Genetic testing confirmed HNPCC. This case highlights the importance of recognizing this rare subtype, its association with hereditary syndromes, and the role of multidisciplinary management and long-term surveillance.