Chromophobe renal cell carcinoma with prominent lymph node metastasis and polysomy of chromosome 21: poorly differentiated form or "presarcomatoid" form?

Lymph node metastasis of chromophobe renal cell carcinoma (RCC) is extremely rare. It has been recently reported that sarcomatoid chromophobe RCC frequently show polysomy of chromosomes 1, 2, 6, 10, and 17. In this article, we report an unusual case of chromophobe RCC. A 42-year-old Japanese woman presented with hematuria and complained of inguinal pain 2 months after the initial symptoms. Radical nephrectomy and renal hilar lymphadenectomy were performed. The tumor was 8 cm in greatest diameter; its cut surface was beige in color. Large metastasis to the renal hilar lymph node was identified. Histological examination of the right renal tumor met the criteria of chromophobe RCC. In addition to histological findings of typical chromophobe RCC, small cell foci, comedo-like necrosis, trabecular growth pattern, and sclerosing stroma were observed. However, no sarcomatoid foci were identified anywhere, despite extensive tumor sampling including lymph node lesions. Immunohistochemically, neoplastic cells were positive for E-cadherin and CD117 (c-kit). Ultrastructurally, tumorous cells contained abundant mitochondria and cytoplasmic microvesicles. Fluorescence in situ hybridization showed monosomy of chromosomes 2 and 10 and polysomy of chromosome 21. Finally, we suggest that this tumor may show the poorly differentiated or presarcomatoid form of chromophobe RCC.