MR FINDINGS INDICATIVE OF HEMOSIDERIN IN GIANT-CELL TUMOR OF BONE - FREQUENCY, CAUSE, AND DIAGNOSTIC-SIGNIFICANCE

OBJECTIVE. We studied the frequency, cause, and diagnostic significanc e of MR findings indicative of large amounts of hemosiderin in giant-c ell tumor of bone. MATERIALS AND METHODS. The clinical, MR, and histol ogic findings in 16 patients with giant-cell tumors of bone were revie wed, Eight tumors occurred in uncommon locations or in patients who we re not in the usual age range; the other eight were more typical. Area s of decreased MR signal intensity considered to be caused by hemoside rin were identified, The number and distribution of RBCs within the tu mor were studied histologically, and the presence of hemosiderin was d etermined on histologic sections made with iron stains. RESULTS. In 10 cases in which MR images showed areas of low signal intensity, large amounts of hemosiderin were noted histologically. The low-signal-inten sity areas were nodular, zonal, whorled, or diffuse and occupied at le ast one fifth of the tumor volume. On histologic examination, many ery throcytes were in direct contact with the tumor cells, and the hemosid erin was seen in both mononuclear and multinuclear tumor cells. CONCLU SION. Hemosiderin is commonly seen on MR images of giant-cell tumors o f bone (63%) and is probably related to the extravasated erythrocytes in the tumor and the phagocytic function of the tumor cells. This MR f inding supports the diagnosis, even in giant-cell tumors in uncommon l ocations or in patients who are not in the typical age range.