Pathologic delineation of the papillonodular type of cystic partially differentiated nephroblastoma. A review of 11 cases

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Abstract
Eleven cases of a previously unrecognized papillonodular variant of cystic partially differentiated nephroblastoma (CPDN) are described. This type of CPDN has all the features of the conventional type of CPDN; however, in addition, there are grossly demonstrable papillonodular projections extending from the septa into the cyst lumina. The septa do not show any expansile tumor masses. Like most cases of the conventional type, this new type of CPDN was usually diagnosed in infants. Nephrectomy (total in 10 and partial in 1) was done in these cases. Additional chemotherapy with or without radiation therapy was given in seven cases. No recurrence was noted during the period extending from 21 months to 8 years in the eight cases in which follow‐up data are available. Nephrectomy with regular follow‐up visits for possible recurrence may be the management of choice. Pathologists should be aware of this variant of CPDN so that overtreatment can be avoided. The revised criteria for CPDN can be summarized as follows: (1) The discrete entirely cystic tumor contains luminal papillonodules in some cases. (2) Septa and the papillonodules, when present, are the only solid portion of the tumor and contain blastemal cells admixed with their normal and aberrant derivatives. (3) The tumor without and with papillonodules is classified as a conventional and papillonodular type of CPDN, respectively.