Objective: Renal cell carcinomas might display foci of calcification and even ossification. This rare event has been reported mostly in the clear cell variant. Herein, we present the case of a 69 year-old man, previously diagnosed with colon cancer, incidentally found to have a calcified mass in the kidney, which was interpreted as non-characteristic for renal cell origin. Results: Radical nephrectomy was performed. A 5.5×5.0× 4.0 cm tumor was found, with a heterogeneous brown cut surface, containing areas of necrotic tissue and extensive calcifications. Histopathologic examination disclosed papillary structures covered by small cells with scant cytoplasm, dispersed among mature bone tissue enclosing marrow elements. Epithelial tumor cells were imunorreactive for cytokeratins, CD10 and PAX2, and negative with HMB-45. Hale`s colloidal iron was negative. Trisomy of 3p, 7p and 17p was detected by FISH. A diagnosis of PRCC type 1, Fuhrman grade 2, with extensive osseous metaplasia was rendered. Conclusion: Ossification of renal cell tumors is rare, occurring mostly in clear cell type and the underlying mechanism is unclear. These tumors show atypical radiological features and might be confused with non-renal cell tumors. To the best of our knowledge, this is the first report of PRCC with osseous metaplasia and bone marrow elements.