Pathological features of renal cell carcinoma incidentally discovered at autopsy

Renal cell carcinomas incidentally discovered at autopsy (IRCs) were retrospectively analyzed to determine whether they had any pathological features differing from clinical renal cell carcinomas (CRCs): From 7,970 autopsy cases, there were 51 cases (0.65%) of renal cell carcinoma (RC) including 42 men and 9 women (ratio 4.6:1). The mean age of RC cases was 66.3 +/- 12.9 (range of 20 to 91 years). Of the 51 RC cases, approximately half of them (25/51) were IRC cases. No difference was shown in age and sex between IRC and CRC cases. Mean tumor size of IRC was 2.6 +/- 2.5 cm in diameter. This was significantly smaller (P less than 0.01) than that of CRC (7.3 +/- 2.8 cm). Histologically, both grade 1 and clear cell type were significantly more predominant among IRC cases than CRC cases (P less than 0.01 and P less than 0.05, respectively). Only one out of 25 cases of IRC had distant metastasis, as compared to 23 out of 26 CRC cases (88.5%). These pathological features indicate that the incidentally discovered renal cell carcinoma may have less malignant potential than clinical tumors. Unexpectedly, the majority of the IRC cases (88.0%) were associated with advanced neoplasia of other sites, as compared to only 19.0% of CRC cases (P less than 0.01).