[Renal cell carcinoma in acquired cystic disease of the kidney manifested by spontaneous renal rupture].

A 67-year-old male had been maintained on hemodialysis for 13 years because of chronic renal failure secondary to diabetes mellitus. The patient was referred to our hospital with sudden right flank pain. Computed tomography revealed multiple cysts in both kidneys and a right massive perirenal hematoma. Although there was no definite evidence of a renal tumor, a right nephretomy was performed. Histological study revealed acquired cystic disease of the kidney (ACDK) with a hematoma containing papillary renal cell carcinoma. He has been free of recurrence for 2 months. To our knowledge, this case is the fourth report of renal cell carcinoma in ACDK manifested by spontaneous rupture in the Japanese literature.