Neoplastic lesions containing both an adenomatous component and a carcinoid component are rare.
To our knowledge, only two such lesions have been reported previously in the large intestine. We report two additional cases to further delineate the histologic features of these lesions and discuss their possible origin. One patient refused repeat colonoscopy at 6 months and subsequently was lost to follow-up. The other patient died 26 months after a hemicolectomy without evidence of recurrence. One lesion represents a collision tumor in which the two histologic components lay adjacent to one another without intermingling.