[A morphological study of renal adenoma and latent renal cell carcinoma in autopsy cases].

PURPOSE We investigated histopathological features of renal adenoma and latent renal cell carcinoma in order to find relationship between these two entities. MATERIALS AND METHODS Renal adenomas or latent renal cell carcinomas found macro- and microscopically in 2,201 autopsy materials were used. Histological examination was focused on the size, and the presence or absence of hemorrhage, necrosis and capsulation of tumors. Additionally, we analyzed morphologically the mean nuclear area (MNA), N/C ratio, mean nuclear volume (MNV) and nuclear roundness factor (NRF) using image analyzer system (CIA-10; Olympus). RESULTS A total of 71 foci of renal cortical tumor was found and classified into renal adenoma (59 foci), latent renal cell carcinoma (8 foci), and intermediate type (4 foci). Intermediate type contained of small element of clear cell and were difficult to distinguish from renal cell carcinoma or ordinary adenoma. The mean diameter of renal adenomas was 1.9 mm. The capsulation was found in only 3 foci (5.1%) of them, and bleeding and necrosis were found in none of them. On the other hand, the mean diameter of latent renal cell carcinoma and intermediate type were 15.7 mm and 6.6 mm, respectively, and larger than that of renal adenomas (p < 0.005). In latent renal cell carcinoma, capsulation were found in all foci, bleeding in 6 (75.0%) and necrosis in 3 (37.5%), and their incidence were significantly higher than those of adenoma (p < 0.005). In intermediate type, capsule and bleeding were found in each two foci. Morphologically, there were significant difference in MNV and NRF but no difference in MNA and N/C ratio between renal adenomas and latent renal cell carcinomas. Intermediate type was larger in NRF compared to adenoma. CONCLUSION Morphological characteristics of intermediate type resemble that of latent renal cell carcinoma in terms of tumor size, the presence of bleeding and capsule and NRF when compared to adenomas. These results suggest that, in some renal cell carcinoma, adenoma might be able to change to carcinoma.