A survey on incidental renal cell carcinoma in Japan.

A survey of renal cell carcinoma detected incidentally (incidental renal cancer) in 116 collaborating institutions was conducted nationwide in Japan between 1980 and 1988. The analysis of 1,428 cases demonstrated a dramatic increase in the frequency of incidental renal cancer from 20 cases in 1980 to 338 cases in 1988. Detection occurred at routine health examinations in 32.8% of the cases and during examinations for unrelated diseases in the remainder. The chief method of detection was ultrasonography (68.2%), followed by computerized tomography (21.8%) and excretory urography (6.4%). Tumor extension was within the renal capsule in 76.5% of the cases and the mean tumor diameter was 5.4 cm. The 5-year survival rate was 76.5% but it was better in cases detected by ultrasonography compared with other methods. These results were compatible with previous reports and suggest that incidental renal cancer detection may improve the prognosis of renal cancer as a whole.