A patient presented with unilateral obstructive nephropathy due to a granulocytic sarcoma (chloroma) arising within the renal pelvis. To the best of our knowledge, granulocytic sarcoma has not previously been described either arising in the urinary system or occurring during induced remission of disease. Even in the absence of other evidence of active disease, with a history of leukemia, this lesion should be considered in the differential diagnosis of collecting system tumors, as recommended therapy is nonsurgical. © 1985 Raven Press, Ltd.
