The frequency of perirenal fat invasion according to size and protrusion shape of renal cell carcinomas

Abstract

Purpose: The perirenal fat surrounding a renal cell carcinoma (RCC) must be preserved during a surgical operation. However, the perirenal fat is often injured during an operation. In such cases, there is the possibility of cancer metastasis. The frequency of perirenal fat invasion and pathological features, according to the size and protrusion shape of RCCs were investigated. Materials and Methods: A retrospective reviewed 93 consecutive RCCs, resected at our institution, between January 1995 and June 2005, was conducted. The frequency of perirenal fat invasion, the pathologic T stage and nuclear grade, according to the size and protrusion shape of RCCs after a radical nephrectomy were also investigated. Eighty three out of 93 lesions were sub classified based on the percentage of the tumor extending from the normal parenchymal border; endophytic-less than 40%, mesophytic-40 to 60% and exophytic-greater than 60%. Results: Of the 93 lesions, 15 (16.1%) had perirenal fat invasion. Of the 38 lesions equal or smaller than 4cm, 2 (5.3%) had perirenal fat invasion, 4 (10.5%) a high T stage and 11 (28.9%) a high nuclear grade. Of the 33 lesions larger than 4cm, but equal or smaller than 7cm, 4 (12.1%) had perirenal fat invasion, 4 (12.1%) a high T stage and 12 (36.4%) a high nuclear grade. Of the 22 lesions larger than 7cm, 9 (40.9%) had perirenal fat invasion, 12 (54.5%) a high T stage and 17 (77.3%) a high nuclear grade. There were statistical differences in perirenal fat invasion, T stage and nuclear grade between lesions equal or smaller than 7cm and those larger than 7cm. The frequencies of perirenal fat invasion for endophytic, mesophytic and exophytic tumors were 12.2, 21.1 and 13.3% (6/49, 4/19 and 2/15), respectively, but there were no statistical differences in the percentages of perirenal fat invasion. The 5-year survival rates for patients without and with perirenal fat invasion were 91.9 and 72.7%, respectively (13=0.039). Conclusions: RCCs with a size of 4cm or smaller have a tendency for low perirenal fat invasion, but 5.3% of small RCCs had perirenal fat invasion. Therefore, an effort should be made to prevent possible metastasis by cautiously preserving the perirenal fat surrounding a renal mass during nephron sparing or minimally invasive surgery.