Heterotopic bone formation in renal cell carcinoma: a diagnostic challenge.

Formation of bone in cases of renal cell carcinoma is a rare finding and only a couple of case reports from Japan and one from India are mentioned in the literature. Calcification inside renal mass has been reported earlier but the prognostic implications have not been clearly elucidated. We report a case which showed heterotopic bone formation (ossification) inside the renal mass and was managed by radical nephrectomy. The histopathology showed clear cell renal carcinoma with multiple centers of ossification in the region of calcification suggesting bone formation. In this case report we discuss bone morphogenetic proteins which have been implicated as a prognostic and causative factor, highlight the difficulties in distinguishing between calcification and bone formation on the basis of radiological investigations and mention the geographic implications of this rare phenomenon which has not been described earlier.