Histopathological study of congenital cystic kidneys with special reference to the multicystic, dysplastic type.

Ten autopsy cases of congenital cystic kidneys were studied by histopathological examination. Eight cases with dysplastic type revealed immature mesoderm, cartilage, localized tight fibrous tissue, hemangiomatous lesion consisting of arterio-capillary-venous elements, extramedullary hematopoiesis, primitive lymph nodes, adipose tissue, and abundant neural tissue in the kidney as well as cystic lesions. These findings strongly suggest that congenital cystic kidneys of dysplastic type are derived from hamartoma or hamartomatous changes chiefly consisting of mesodermal tissue, most of which corresponds to tissue anomaly and is very close to the aberrant form of Wilms' tumor. The presence of focal fibrosis and lymphoid cell infiltration forming focal renal tissue destruction suggest local disturbance of tissue differentiation due to some casual elements. As common feature of this type, it is revealed that the babies show lower weight for their fetal ages and die shortly after birth or are delivered as still birth due to hypoplasia and atelectasis of the pulmonary tissue.