Multilocular renal cyst.

A case of multilocular renal cyst histologically consistent with clear cell carcinoma is reported. This case is unusual in that the cyst had features indicative of a developmental malformation superimposed by a neoplasm. The controversy over the pathogenesis of multilocular cyst--neoplasm versus developmental anomaly--is unsettled. This case illustrates the possibility that multilocular cysts can be developmental defects which subsequently become the origin of neoplastic transformation of the dysgenetic tissue.