Multilocular cystic renal cell carcinoma with focus on clinical and pathobiological aspects.

Multilocular cystic renal cell carcinoma (MCRCC) accounts for approximately 1 to 2% of all renal tumors. This tumor is currently classified as a subtype of clear cell RCC. Clinically, the majority of these tumors are incidentally found. Macroscopically, the tumor is well demarcated and consists of various-sized cysts. The fibrous septa are generally thin and there is no discernible expansile nodule. Microscopically, the cyst walls are lined with tumor cells with clear to occasionally slightly eosinophilic cytoplasm. The Fuhrman nuclear grade is generally low and usually corresponds to grade 1. The deletion of chromosome 3p was identified in most tumors using FISH analysis and VHL gene mutation was identified in 25% of MCRCC. As MCRCC generally exhibits a low stage of TNM classification, the great majority of these tumors have a favorable clinical course. To date, there are no reports of metastasis, vascular invasion or sarcomatoid change in MCRCC. Accordingly, nephron sparing surgery is first recommended as a therapeutic strategy.