Chromosome anomalies suggestive of malignant transformation in bilateral renal oncocytoma.

A patient with bilateral renal oncocytoma is presented, and the clinical, radiological and pathological characteristics of this uncommon, clinically benign renal tumor are discussed briefly. Chromosomal analysis studies revealed the following clonal abnormalities: trisomy of chromosome 7, and monosomy of chromosomes 3 and 14, and the X chromosome. A possible clonal abnormality of chromosome 10 and 3 nonclonal anomalies also were identified. The same anomalies were present in both tumors. These karyotypic anomalies are compatible with malignant transformation of the cells of these tumors and, since benign tumors rarely are associated with demonstrable cytogenetic changes, they suggest that oncocytoma, although clinically benign, may have malignant potential.