Diagnosis:
Chromosome Changes in Renal Cell Carcinoma
• Renal cell carcinoma (RCC) is a heterogeneous group of epithelial tumors in terms of histology and clinical behavior. RCCs are classified based on cytology, cell type of origin, and genetic changes.
• Major classes of RCC are clear cell, papillary, chromophobe, oncocytoma, collecting duct carcinomas, sarcomatoid transformation in RCC, and mucinous tubular and spindle cell carcinoma. Although most RCCs are sporadic, syndromic forms have been reported for each of the major histologic types.
• Cytogenetic alterations are highly specific to each major histologic type of RCC and are of diagnostic relevance.
• Clear cell RCC arising from mature renal tubular cells represents approximately 75% of all RCCs. Clear cell RCC is characterized by deletions on chromosome 3p. Several common regions of deletion at 3p14, 3p21, and 3p25 were identified. The 3q21 deletion is obligatory for classification as a clear cell RCC. Additional abnormalities include partial trisomy of 5q and gain of chromosomes 12 and 20.
• Papillary RCC represents about 10% of all RCCs. Trisomy or tetrasomy of chromosome 7 and trisomy 17 are characteristic features of papillary RCC. Gain of chromosomes 12, 16, and 20 is present in aggressive tumors.
• Chromophobe-type RCC represent 5% of all RCCs. Cytogenetically, chromophobe RCC exhibits a modal chromosome number of 38-39 with frequent losses of chromosomes 1, 2, 6, 10, 13, 17, and 21.
• Renal oncotyoma is a benign neoplasm. Chromosome abnormalities are seen in approximately 50% of oncocytomas. Loss of chromosomes 1 and 14, and loss of the Y chromosome in males, are seen in one subset of tumors. In a second subset, translocations at 11q13 are seen; 11q13 rearranges with many different chromosomes in this setting.
• Mucinous tubular and spindle cell carcinoma is a distinct form of RCC. Cytogenetic characteristics of very few cases have been reported. Loss of chromosomes 1, 14, and 15 has been described.
