A patient with tumoral calcinosis involving the buttock and ischial bone is presented. Bone marrow involvement and a pattern of septal enhancement on MR imaging after intravenous administration of Gd-DTPA were very suggestive of a diagnosis of a chondro(sarco) matous musculoskeletal tumor. The absence of an underlying metabolic disorder, the appreciation of fluid-calcium levels within the lesion and knowledge of the macroscopic and microscopic appearance of this disorder have led to the correct diagnosis in this case.