Clear cell renal cell carcinoma with osseous metaplasia: Two extremely rare cases and review of the literature.

Renal cell carcinoma is constantly associated with calcification, but ossification is extremely scarce. METHOD: We retrospectively analyzed two cases with clear cell renal cell carcinoma with osseous metaplasia. RESULTS: We criticized the oldest case of woman whose a 32x31mm irregular renal mass with calcifications and we also mentioned about a diffusely calcified mass of 90 mm of a 68-year-old male patient. The histopathological examinations of both were reported as clear cell carcinoma with metaplastic bone formation. CONCLUSION: Although there are no definitive data on prognosis and follow-up due to the low number of cases; this entity usually occurs with early stage disease and a favorable prognosis as in our cases. While the prognostic importance of osseous metaplasia existence in renal cell carcinoma is controversial, such that can safely be managed with nephron sparing surgery in appropriate cases. As the number of cases and follow-up periods increased; more definitive information will be obtained.