OBJECTIVETo assess the clinicopathological features and molecular genetic changes of multilocular cystic renal cell carcinoma (MCRCC).

METHODSAll the data reviewed were from the files of pathology department of Changhai hospital collected from 1990 to 2006. In totally 706 cases of renal cell carcinoma studied, there were 21 MCRCC cases identified. The clinical and pathological features were assessed, immunohistochemical staining was performed, and loss of heterozygosity (LOH) and microsatellite instability (MSI) were assessed using four microsatellite markers on chromosomes 3, 9 and 14.

RESULTSOf the 21 patients, the age ranged from 34 to 72 years (mean 50 years), 19 were male and two female. Tumors were found incidentally in 18 patients during physical examination, three patients had anemia or microhematuria. Among the 21 patients, 10 tumors were in the left kidney and 11 in the right. Eighteen patients were stage T1, two stage T2, and one stage T3 with perinephric tissue involvement. Follow up information was available in 20 patients, all showed no evidence of tumor recurrence or metastasis. Grossly, the tumor size ranged from 0.3 cm to 10.0 cm in the greatest dimension, consisting of multilocular cysts with variable sizes which contained light yellow, colloid or hemorrhagic fluid. The septae varied in thickness (ranged 0.1 cm to 0.5 cm, mean 0.2 cm). Microscopically the cysts were lined by single to multilayered epithelial cells with clear or lightly eosinophilic cytoplasm. There were clusters of clear cells seen in the septae stroma. Sixteen tumors were of Fuhrman grade 1, and five were of Fuhrman grade 2. Immunohistochemically, the clear cells were positive for vimentin, ABC, CAM5.2 and EMA. Six samples were positive for CD10, and 16 were positive for NSE. Among 21 patients, PCR amplification was successful in 11 patients. Microsatellite alterations were found in five patients. LOH was observed in 3 of 11 MCRCC (27%), two were at D3S1560 locus, and one at D14S617 locus. MSI frequency was identified in 2 of 11 MCRCC (18%), locating at D9S168 or D14S617 locus, respectively.

CONCLUSIONSMCRCC is an uncommon tumor of kidney, constituting 2.9% of all RCC enrolled into the study. It has distinctive clinical and pathological characteristics with an excellent outcome. Results indicated that MCRCC is a rare entity with low malignant potential.