AbstractA 67 year old white male presented with melena and weakness. Colonoscopy revealed a polypoid rectal mass, proven by biopsy to be a moderately well differentiated rectal adenocarcinoma. Histopathologic evaluation of the resected specimen revealed that the neoplastic disease was associated with malacoplakia. The relationship between malacoplakia and various neoplastic and non-neoplastic conditions are discussed. (The J Histotechnol19:145, 1996)