Presacral myelolipoma.

Extramedullary tumors of hematopoietic tissue can be divided into two categories: those associated with a bone marrow disorder, myelolipomas which have no apparent relation to a bone marrow disorder. The etiology of myelolipoma is unknown and the vast majority are adrenal in location. Extramedullary myelolipomas are usually presacral in location and none of the approximately ten reported cases has been diagnosed before surgery. Although radiographic and ultrasound features of myelolipomas are relatively characteristic, they are not specific and biopsy is required for diagnosis. Microscopic diagnosis requires demonstration of benign lipomatous tissue admixed with cellular hematopoietic tissue resembling normal bone marrow. This study reports a patient with presacral myelolipoma and an unusual finding of urinary retention and azotemia associated with compression of urinary bladder neck by the myelolipoma.