Hypernephroma arising in wall of simple renal cyst

An unusual case of hypernephroma arising from the wall of a simple renal cyst is presented. Despite prior controversy as to the existence of this entity continuity between normal and neoplastic cells lining the cyst wall was demonstrated thus confirming this lesion as a distinct entity. Furthermore, we wish to direct attention to the limitations of biochemical and cytologic analysis of renal cyst fluid in distinguishing benign and neoplastic lesions.