[Extracapsular tumor invasion in renal cell carcinoma: with special reference to limitation of surgical enucleation].

To elucidate the feasibility of surgical enucleation, the incidence of extracapsular tumor invasion in 30 cases of renal cell carcinoma with a diameter less than 5 cm was examined, based on the classification of extracapsular tumor invasion into three patterns, namely microinvasion, nodular invasion, and daughter tumors. Of the 30 cases of renal cell carcinoma, 22 cases (73%) revealed extracapsular tumor invasion. And the incidence of microinvasion, nodular invasion and daughter tumors was 7 cases (23%), 9 cases (30%) and 6 cases (20%), respectively. But the incidence of these three patterns of extracapsular tumor invasion correlated neither with the size of renal cell carcinoma nor with pT classification. There was a tendency for extracapsular tumor invasion to occur near the renal hilar site of the renal cell carcinoma, where the tumor vessels were rich, penetrated and twined around the tumor capsule, resulting in the disruption of the tumor capsule. These three patterns of invasion was located within 1 cm in distance from the tumor capsules in all cases. In conclusion, because of limited radicality achieved by tumor enucleation even in the case of pT1, partial nephrectomy was recommended in the presence of a normal contralateral kidney.