[A clinico-pathological study of small renal cell carcinoma]

Between 1960 and 1989, 50 patients with small renal cell carcinoma measuring below 3 cm in diameter were examined. Among them, 31 patients were nephrectomized, but in 19 patients, the renal cell carcinoma was found first at autopsy. The average tumor diameter of the unrecognized ones was smaller than that of nephrectomized patients with the minimum of 0.4 cm. Forty-one patients had clear cell carcinoma, 9 granular cell carcinoma, 40 grade 1 tumor, and 10 grade 2 tumor. The grade 3 tumor was not found in our study. Three out of the 50 patients had distant metastasis at the time of operation or autopsy. Six patients had microscopic tumor thrombi just close to the tumor pseudo-capsule. Two patients had apparent tumor thrombi in the main renal vein. The smallest tumor that showed microscopic tumor thrombi measured 1.5 cm in diameter. The incidence of tumor thrombi was correlated with tumor diameter. The step sections by 4 mm thick of nephrectomized specimens were examined on 16 patients. The daughter tumor was found in two patients. The tumor thrombi had close relationships with the presence of distant metastasis (p less than 0.001) and/or the daughter tumor (p less than 0.01). In conclusion, small renal carcinoma measuring less than 1.5 cm in diameter was considered to be treated by conservative surgery.