Necrotizing fasciitis of the thigh should raise suspicion of a rectal cancer.

Perforation of rectal cancer usually occurs intraperitoneally. Extraperitoneal perforation is rare and usually presents as perineal sepsis, leading to diagnosis and urgent surgical management plus antibiotic therapy. We report the case of a patient presenting with a perforated rectal carcinoma which presented as necrotizing fasciitis of the right thigh.