Heterotopic bone formation in clear cell renal cell carcinoma

ABSTRACT Clear cell renal cell carcinoma is associated with calcium deposition in a significant percentage of patients. However, frank ossification within a tumor is extremely rare. We report a case of a 41-year-old male with a slow-growing left renal mass who underwent minimally invasive nephron-sparing surgery. Final pathology revealed clear cell renal cell carcinoma with focal areas of heterotopic bone formation. While prognostic implications of this variant are unclear, patients with renal cell carcinoma with osseous metaplasia can present with slow growth kinetics and early-stage disease.