We report a case of a tumoral calcinosis mimicking the appearance of recurrent osteosarcoma of the left femur and tibia in a 29-year-old woman with a history of osteosarcoma and chronic renal failure. Both processes can appear radiographically and histologically similar. Due to loosening of the orthopedic hardware, our patient underwent surgical revision and biopsy. We review the imaging appearances of both entities as well as the underlying mechanism of tumoral calcinosis secondary to renal disease. We also discuss how PET and CT imaging can aid in differentiation of these processes and possibly prevent surgical biopsy in other cases.