A Rare Case of Squamous Cell Carcinoma of the Gallbladder Presenting as a Bleeding Colonic Mass.

Gallbladder carcinoma (GBC) is the most common malignancy of the biliary tract, with adenocarcinoma being the predominant histological subtype. Squamous cell carcinoma (SCC) is rare, accounting for approximately 1%-4% of gallbladder carcinomas, and is characterized by aggressive local invasion and poor prognosis. We report a 53-year-old man with a one-year history of recurrent painless lower gastrointestinal bleeding and a six-month history of progressive constipation, abdominal bloating, and unintentional weight loss. His bleeding had previously been attributed to a known grade 4 hemorrhoid. Colonoscopy revealed a friable, bleeding mass at the hepatic flexure in addition to non-bleeding grade 4 hemorrhoids. Histopathological examination of the colonic biopsy demonstrated moderately differentiated SCC. Immunohistochemistry was positive for cytokeratin 7 (CK7) and p63, and negative for cytokeratin 20 (CK20), hepatocyte paraffin 1 (HepPar-1), and alpha-fetoprotein (AFP). Contrast-enhanced computed tomography (CT) subsequently demonstrated a large heterogeneous gallbladder mass with direct invasion of the adjacent liver and hepatic flexure, rendering the tumor unresectable. The integrated clinicoradiological and pathological findings supported a diagnosis of locally advanced gallbladder SCC with direct extension into the colon. The patient received gemcitabine and oxaliplatin chemotherapy, followed by endoscopic retrograde cholangiopancreatography (ERCP) with biliary stent placement and palliative surgical management for persistent lower gastrointestinal bleeding. This case highlights the diagnostic challenge posed by gallbladder SCC presenting as a bleeding colonic mass. Squamous carcinoma identified in a colonic lesion should prompt consideration of an extra-colonic primary, with immunohistochemistry interpreted alongside clinical and radiological findings. Persistent gastrointestinal bleeding warrants thorough evaluation even when an apparent anorectal source is present.