Adult rhabdoid renal cell carcinoma

Pediatric rhabdoid tumor of the kidney is regarded as a distinct neoplasm, whereas rhabdoid differentiation in adult renal cell carcinoma is usually found in association with conventional (clear cell) tumor, from which it is thought to evolve. To further characterize the rhabdoid phenotype in adult renal cell carcinoma and to determine its origin by genetic analysis. We performed histologic, immunophenotypic, and genetic analyses on 5 cases of adult renal cell carcinoma with rhabdoid differentiation, 3 samples of adjacent conventional (clear cell) tumor, and 6 conventional (clear cell) control tumors. Rhabdoid tumors differed from conventional (clear cell) carcinoma as follows: (1) macroscopically, rhabdoid tumors were solid white uniform masses; (2) microscopically, they had large rhabdoid cells with abundant eosinophilic cytoplasm, reduced lipid content, and the absence of a branching vascular pattern; and (3) biologically, they had a high metastatic potential. Despite these differences, loss of chromosome 3p in both the rhabdoid and clear cell carcinoma samples from 1 patient suggested a clonal origin. An identical mutation of the VHL gene in both rhabdoid and clear cell tumor samples from 2 patients confirmed a clonal origin for the histologically distinct tumor types in those cases. Adult rhabdoid renal cell carcinoma can in some cases arise from conventional (clear cell) renal carcinoma and should be considered a clinically important form of renal cell carcinoma separate from, but analogous to, sarcomatoid change.