Small clusters and aggregates of tumor cells are scattered in a background of myxoid stroma which usually contains a sprinkling of mast cells and chronic inflammatory cells. Some of the tumor cells seem to be arranged concentrically around arterioles. The patient was a 15 y/o previously healthy female who was found to have elevated blood pressure during a routine physical examination for sports. She also gave a brief history of headaches. Abdominal CT scan showed a 3.0 cm cortical mass in the left kidney. Laboratory evaluation showed increased plasma renin activity, hypokalemia, and normal urinary catecholamines. Selective renal vein renin measurements showed lateralization to the left kidney and a diagnosis of juxtaglomerular cell tumor was rendered. The patient underwent partial nephrectomy which cured her hypertension.