Non-Mass-Forming Myeloid Sarcoma of the Colon Presenting With Diarrhea.

A female patient in her mid-70s, with a history of diverticulosis, presented with a 2-month history of severe diarrhea, left lower quadrant abdominal pain, decreased appetite, and fever. She was treated for diverticulitis, but did not improve. Subsequent workup revealed leukocytosis and circulating myeloblasts on a peripheral blood smear. Bone marrow evaluation and flow cytometry confirmed the diagnosis of acute myeloid leukemia. Abdominal computed tomography and sigmoidoscopy were performed for her persistent diarrhea. While both failed to show an obvious mass or anatomical abnormality, pathology from the colorectum showed infiltration by leukemic cells consistent with myeloid sarcoma. The diarrhea improved with acute myeloid leukemia chemotherapy.