Renal cell carcinoma sub-typing by histopathology and fluorescence in situ hybridization on a needle-biopsy specimen

OBJECTIVE To determine the subtype of renal cell carcinoma (RCC) on needle-core biopsies of renal masses using histopathology and fluorescence in situ hybridization (FISH), and to evaluate the use of interphase FISH to augment the accuracy of needle-core biopsies. PATIENTS AND METHODS Histology correlates with prognosis in RCC but, historically, biopsies are inaccurate for histological subtype. As histological subtypes of RCC have distinct cytogenetic abnormalities (loss of 3p in clear cell, trisomy 7 or 17 in papillary and widespread chromosomal losses in chromophobe), we hypothesized that FISH would improve the accuracy of biopsies. Forty patients with renal masses underwent nephrectomy, yielding 42 tumours. Needle-core biopsies were taken of the mass immediately after surgery. Interphase FISH was performed on one core for chromosomes 3, 7, 10, 13, 17, and 21 and the locus 3p25-26. Histopathology was performed on a second core. Results were compared in a 'blinded' fashion with final pathology. RESULTS In all, 36 of 42 masses were RCC or oncocytoma. Histopathology of the biopsy correctly identified the tumour subtype in 27 (75%), while four (11%) were incorrectly classified and five (14%) were inadequate for diagnosis. With the addition of FISH, 31 (86%) were correctly subtyped, while two (6%) were incorrect and three (8%) were inadequate. In cases with adequate tissue, histology alone was 87% accurate, while the combined method was 94% accurate. CONCLUSION Needle-core biopsy of renal tumours provides adequate material for evaluation of histological subtype. Adding FISH to histopathology might improve the accuracy of kidney tumour biopsies, providing important prognostic information that can guide management decisions.