Malignant tumors associated with carcinoid tumors of the gastrointestinal tract.

Twenty-three associated malignant neoplasms mostly adenocarcinomas were recognized in 96 patients with gastrointestinal carcinoid tumors, between 1968 and 1977 at the University of Rochester Medical Center. Associated malignancies were present in 17 patients, affected various organs and led to an early death even though the carcinoid tumors generally remained localized. There was a 36% incidence of a second malignant neoplasm in patients with ileal carcinoid, but no second tumor in patients with carcinoid of the rectum. The presence of a carcinoid tumor should alert the physician to search for a second neoplasm.