Primary Signet-Ring Cell Carcinoma of the Colon: A Rare and Aggressive Tumor

We report the case of a 50-year-old man who presented with progressive abdominal distension, weight loss, and ascites. Imaging revealed ileocecal wall thickening associated with peritoneal involvement. Colonoscopy demonstrated a circumferential, stenosing, ulcerative lesion in the cecum that was friable and could not be traversed by the endoscope. Histopathological examination of biopsy specimens confirmed signet-ring cell carcinoma. Upper gastrointestinal endoscopy showed no evidence of a gastric primary tumor, and computed tomography excluded distant metastasis, supporting a primary colonic origin. The patient was started on XELOX chemotherapy (capecitabine and oxaliplatin). This case highlights the diagnostic challenge of this entity, particularly in the presence of atypical features.