Myeloid sarcoma of the urinary bladder and epididymis as a primary manifestation of acute myeloid leukemia with inv(16).

Myeloid sarcoma (MS) of the lower urinary tract is rare. We describe a 47-year-old man with hematuria, who was subsequently found to have MS involving bladder and epididymis. The neoplasm was composed predominantly of blasts that expressed CD68, CD117, myeloperoxidase, and lysozyme, with occasional immature eosinophils. Although blood and bone marrow examinations showed no morphologic evidence of leukemia, conventional cytogenetic studies of marrow demonstrated inv(16)(p13q22) in 4 of 20 metaphases; fluorescence in situ hybridization of the bladder neoplasm also showed inv(16). Following chemotherapy, the patient has been in complete remission for 32 months. In our literature review, we identified 7 cases of MS involving bladder, only 3 without evidence of an associated myeloid neoplasm in marrow, none with cytogenetic data. A high index of suspicion is required to establish the diagnosis of MS involving bladder. Cytogenetic analysis is useful for both demonstrating minimal marrow disease and classifying MS in paraffin-embedded tissue sections.