Basaloid Squamous Carcinoma arising at Splenic Flexure of Colon

Basaloid squamous carcinoma occurs most commonly in the upper aerodigestive tract. In the colon, the most common location is in the anal canal and is rarely reported proximal to the anal verge. Six cases are reported in the published literature, of which five are located distal to the splenic flexure. Outside the anal canal, it has been postulated that they arise from the basal cells, squamous metaplastic cells, or the cloacogenic embryologic cell rests. We report a case of a 57-year-old male patient who presented with short duration of abdominal pain and weight loss. Computed tomography (CT) abdomen revealed an irregular circumferential thickening in the terminal transverse colon, splenic flexure, and proximal descending colon. Colonoscopy showed a stricture in the splenic flexure, which was suspected for malignancy. Endoscopic biopsy was reported as poorly differentiated carcinoma. Left extended hemicolectomy was done, and a diagnosis of basaloid squamous carcinoma was made on histopathology. The tumor cells were positive for P63, CK 5/6; focally for CDX2; and negative for CK20, chromogranin, and CD56, confirming the histopathological diagnosis of basaloid squamous carcinoma. The patient is currently on adjuvant chemotherapy.