Incidentally diagnosed renal cell carcinoma.

: We analyzed the incidence, sex and age distribution, diagnostic methods and survival rate of incidentally detected renal cell carcinomas (RCCs) and compared these factors with those of symptomatic RCCs. Of 141 patients with RCC treated between 1980 and 1989, 44 cases (31.4%) were incidentally detected. Thirty-one of these 44 cases were diagnosed by abdominal ultrasonography. The age of the incidental cases was significantly higher than that of the symptomatic ones (p = 0.045), particularly in male patients (p = 0.049). The tumor size in incidental cases was smaller and tumor stage earlier (p less than 0.0001). Moreover, the grade of malignancy was significantly lower, and clear cell type tumors were more frequently detected in the incidental cases. No difference was observed between the survival rates of incidental and symptomatic cases with stage 1 or 2 tumors. Of the incidental cases with stage 1 or 2, however, no patient with a tumor 3 cm or less in diameter has died. In conclusion, abdominal ultrasonography is a useful tool to detect RCC at an early stage, and patients with a relatively small tumor tend to have a good prognosis.