A case of leukemia of the appendix presenting as acute appendicitis

A 71-year-old man was admitted to our hospital because of right lower abdominal pain. He was suspected of having acute appendicitis and soon after admission, appendectomy was performed. Macroscopically, the appendix was greatly swollen and reddened, but had no abscess. Microscopically, polymorphonuclear leukocytes were not found, but diffuse infiltration of atypical cells was observed. Examination of a bone marrow aspirate revealed 74% blasts that were peroxidase stain positive. We diagnosed acute myelogenous leukemia (FAB classification, M2). He received induction chemotherapy, but died 49 days after admission. Leukemic cell infiltration of the appendix is rare and acute appendicitis as the initial manifestation of leukemia is even rarer.