Lymphangitic Retroperitoneal Carcinomatosis Occurring From Metastatic Sarcomatoid Chromophobe Renal Cell Carcinoma

A 45-year-old man with left renal mass underwent nephrectomy to reveal a 20-cm tumor diagnosed as sarcomatoid chromophobe renal cell carcinoma. Lymph node metastasis of chromophobe and sarcomatoid components, disseminated tumor in retroperitoneal fat, lymphatic vessels, and perirenal adipose tissue in lymphangitic carcinomatosis pattern were identified. Chromophobe epithelial cells were positive for epithelial membrane antigen, c-Kit, and cytokeratin 7; sarcomatoid cells were positive for CD10 and smooth muscle antigen with high proliferation index. Chromophobe epithelial cells had loss of heterozygosity in chromosomes 1p and 1q, whereas sarcomatoid cells had loss of heterozygosity in 3p, 1p, and 1q. In conclusion, sarcomatoid chromophobe renal cell carcinoma has aggressive biologic behavior and potential to metastasize in unusual patterns.