A case of perforated small bowel adenocarcinoma presenting as first symptom of Crohn's disease is reported in a 53 years old male patient with abdominal pain and alteration of bowel habits. Endoscopic bioptical sampling demonstrated a Crohn's disease in active stage. The patient underwent medical therapy with resolution of the complained symptomatology; 20 days after discharge the patients is rehospitalized for acute abdomen. A narrowing perforated neoplasia in terminal ileum was discovered at laparotomy. Diffuse peritonitis and metastatic peritoneal implantations were also revealed. An ileocolic resection is performed with ileo-transverse colon anastomosis. The patient dies 4 months later for advanced disease.