Renal cell carcinomas in children and young adults - Increased incidence of papillary architecture and unique subtypes

Renal cell carcinomas in children and young adults are rare, and the pathol ogic features of these tumors have not been well described. We reviewed 24 renal cell carcinomas in children and young adults ages 6 to 29 years, 14 o f whom were younger than 18 years of age. Fourteen were female. In 19 (79%) of 24 cases, the tumor met histologic criteria for papillary renal cell ca rcinoma, with at least 50% papillary architecture. Four of the remaining fi ve cases were typical clear cell tumors in patients known to have von Hippe l Lindau syndrome, and one case was of chromophobe type. In the papillary t umors, calcifications, high nuclear grade, extracapsular extension (America n Joint Commission on Cancer stage T3), and lymph node metastases were comm on. Among these papillary tumors, four distinct histologic patterns could b e identified. Collecting duct-like tumors (tno cases) involved the large co llecting ducts, were multifocal and predominantly papillary. and had focal tubular and solid areas. These tumors were reactive for epithelial membrane antigen (EMA) and keratins, including CK7, but negative for filer europeau s and high molecular weight keratin 34BE12. Voluminous cell tumors (four ca ses) were composed of cells with extremely voluminous clear cytoplasm and, although predominantly papillary, had areas that also resembled clear cell tumors. These tumors were reactive for keratins AE1/AE3 but were otherwise negative for all other keratins, EMA, and U. europeaus. One of these tumors showed an X;7 translocation. Adult type tumors (12 cases) resembled papill ary tumors of adults. These tumors were reactive for EMA and keratins, incl uding CK7, and all but one were negative for U. europeaus and keratin 34BE1 2. This last case had trisomies of chromosomes 7, 16, 17, and 20. The final neuroendocrinelike case was multifocal, organoid, and composed of nests of small cells in a neuroendocrinelike pattern. Three of 13 patients were ali ve with disease at last follow-up, and three additional patients died of di sease, all within 2 years. Progression was highly associated with lymph nud e involvement at the time of resection. We conclude that the clinicopatholo gic features of renal cell carcinomas in children and young adults differ f rom those arising in older adults. These tumors are characteristically high -grade, high-stage, papillary tumors with numerous calcifications, and seve ral subtypes can be identified based on histologic, immunohistochemical, an d cytogenetic features. Some subtypes appear to be unique to this age group .