Multilocular renal cyst. Scanning and transmission electron microscopic observations.

A multilocular renal cyst in a boy aged one year and four months is presented, with particular attention being paid to the nature of the epithelial lining cells. Light and transmission electron microscopy showed the cyst to be lined by a single layer of flattened or cuboidal epithelial cells of relatively uniform morphology. Neither embryonic elements nor nephroblastomatous foci were noted in the intervening stroma. The scanning electron microscopy showed hitherto undescribed surface morphological features of the epithelial lining cells: They were characterized by the presence of one or, occasionally two centrally positioned long cilia and by variably oriented microvilli. The observations presented here suggested that the lining cells of the cyst most closely resembled the principal cells of the collecting ducts, especially those located in the inner medulla of the kidney. An unexpected finding was the additional occurrence of a giant bullous lesion in the right lung of this patient.