Chromosome 1 Analysis in Chromophobe Renal Cell Carcinomas With Tissue Microarray (TMA)-facilitated Fluorescence In Situ Hybridization (FISH) Demonstrates Loss of 1p/1 Which is Also Present in Renal Oncocytomas

Abstract

Morphologic overlap between chromophobe renal cell carcinoma (ChRCC) and renal oncocytomas (RO) has been widely recognized. Whether these tumors are genetically related and represent a spectrum of benign to malignant tumor progression remains an open question. We previously showed by conventional cytogenetics and fluorescent in situ hybridization (FISH) that the most common chromosomal abnormality in RO is loss of chromosome 1 or 1p. In this study, we evaluated chromosome 1 in ChRCC using the same set of FISH probes. Twenty-one ChRCCs from 13 men and 8 women were studied. Formalin-fixed, paraffin-embedded tissue blocks were used to construct tissue microarrays. A subtelomeric 1p36.3 probe was used in tandem with 1q25 probes for FISH studies. The patients ranged in age from 34 to 82 years (mean 62.8 y, median 61 y). FISH analysis showed an abnormal chromosome 1 in 20/21 (95%) ChRCCs as follows: 18 tumors (85%) had loss of entire chromosome 1, 2 tumors (10%) had loss of 1p36.3 only, and 1 tumor (5%) was apparently diploid for chromosome 1. In this study, 95% of ChRCCs showed abnormality of chromosome 1 by FISH. The progression of chromosome 1 abnormalities, from diploid to loss of 1p to loss of entire chromosome, is also present in oncocytomas. These results provide further evidence to support a genetic similarity between chromophobe carcinoma and oncocytoma. Whether abnormalities of chromosome 1 are associated with RO tumorigenesis or its progression to carcinoma requires further studies.