Numerical chromosomal aberrations in papillary renal cortical tumors - Relationship with histopathologic features

Previous studies have indicated that a combined trisomy of chromosomes 7 and 17 is a constant finding in papillary renal cortical adenomas and that papillary renal cell carcinomas are marked by additional trisomies such as trisomy 12, 16, and 20. The aim of our study was to compare this cytogenetic classification of papillary renal cortical tumors with conventional histopathologic classification. We performed interphase cytogenetics with enumeration probes for chromosomes 7, 12, 16, 17, and 20 on 41 papillary tumors found in 21 nephrectomy and 10 autopsy kidneys. A total of 38 tumors harbored gains of chromosomes 7 or 17, and most of these showed a trisomic signal distribution. The three tumors with normal copy numbers for chromosomes 7 and 17 were a papillary grade-2 carcinoma, a small adenoma (both with distinctive oxyphilic cytoplasm), and a papillary carcinoma with focally clear cells. Gains for chromosomes 12, 16, or 20 were found in 21 tumors and were significantly associated with the presence of histologic criteria of malignancy (P<0.0001). Histopathologic and cytogenetic features of malignancy were found in eight tumors smaller than 10 mm. There is a good agreement of cytogenetic and histopathologic criteria of malignancy in papillary renal cell tumors. Interphase cytogenetics might give useful additional information in cases of doubt or when only small biopsy specimens are available.