Purpose: Metanephric adenoma has recently been recognized as a unique renal tumor characterized by an unusual degree of cellular differentiation and maturation. We recently studied metanephric adenoma using metaphase analysis and observed concomitant chromosome Y loss and chromosome 7 and 17 gain. To determine if these chromosomal anomalies are consistently present in renal metanephric adenoma, we studied all 11 tumors in the pathology tissue registry at our institution using fluorescence in situ hybridization (FISH).
Materials and methods: FISH, using deoxyribonucleic acid probes for chromosomes 1, 7, 8, 17, X and Y, was performed in isolated nuclei from 11 paraffin embedded renal metanephric adenoma specimens.
Results: Of the 11 tumors (73%) 8 demonstrated chromosome 7 and 17 gain by FISH, and the remaining 3 were found to have an apparently normal chromosomal content. Of the 8 tumors (75%) from men showed 6 chromosome 7 and 17 gain with Y chromosome loss. Of the 3 tumors (33%) from women 1 had chromosome 7 and 17 gain with X chromosome loss, while 1 had chromosome 7 and 17 gain without sex chromosome aneusomy. Metaphase analysis performed on 2 tumors revealed chromosome 7 and 17 gain and Y chromosome loss in 1, and no apparent, chromosome anomaly in the other, confirming the results of FISH analysis.
Conclusions: FISH analysis of renal metanephric adenoma identified frequent chromosome 7 and 17 gain and sex chromosome loss. These results are consistent with a clonal neoplastic disorder in which chromosomes 7, 17, X and Y are likely to be involved in the pathogenesis of this tumor. These characteristic chromosomal alterations have also been observed in papillary renal cell adenoma and papillary renal cell carcinoma, providing evidence that these tumors may be related.