A Gut Feeling: Metastatic Colorectal Adenocarcinoma With Dirty Necrosis in a Young Adult Without Risk Factors.

Colorectal cancer (CRC) is traditionally considered a disease of older adults with established risk factors such as family history, inflammatory bowel disease, or hereditary syndromes. However, CRC is increasingly being diagnosed in individuals younger than 50 years of age, a phenomenon referred to as early-onset CRC (EOCRC). These patients frequently present with advanced disease and often lack classic predisposing factors, posing diagnostic and clinical challenges. We report the case of a 38-year-old male patient with no personal or family history of malignancy who presented with approximately four weeks of abdominal pain, tenesmus, and hematochezia. Imaging revealed circumferential rectal wall thickening with a large hepatic mass and lymphadenopathy. Colonoscopy demonstrated a nearly circumferential friable rectal mass extending into the anal canal. Histopathologic evaluation of the liver lesion revealed metastatic adenocarcinoma characterized by extensive dirty necrosis, strongly favoring a colorectal primary. Serum carcinoembryonic antigen (CEA) was markedly elevated. Based on imaging and histopathologic findings, the disease was staged as stage IV CRC with hepatic metastasis. This case highlights the aggressive nature of EOCRC, the diagnostic importance of pathologic features such as dirty necrosis in determining tumor origin, and the need to reconsider diagnostic thresholds when younger adults present with gastrointestinal symptoms.