Infliximab is an effective agent in the treatment of patients with Crohn’s disease. Therapy with infliximab is generally well tolerated but there are concerns about its effects on the incidence of cancer. This case report refers to a 47-year-old patient with long-standing Crohn’s disease, without a family history of colorectal cancer, who had a previous diagnosis of low-grade dysplasia that was not confirmed in subsequent studies, and was diagnosed with adenocarcinoma of the colon with peritoneal invasion after the fourth infusion of infliximab.