The Role of Tc-99m MDP and Ga-67 Imaging in the Clinical Evaluation of Malignant Fibrous Histiocytoma

The purpose of this study was to evaluate the value of bone and Ga-67 imaging in patients with malignant fibrous histiocytoma (MFH). Thirty-four patients with biopsy-proven MFH were studied. Of these patients, 15 underwent Ga-67 imaging, 26 underwent Tc-99m MDP imaging, and 7 underwent both imaging procedures. In evaluation of the primary tumors, intense Ga-67 uptake was observed in 14 of 15 patients with a diagnostic sensitivity of 93.3%. However, positive bone imaging results were observed in only 10 of 26 patients with a diagnostic sensitivity of 38.5%. Most of these were secondary to Tc-99m MDP uptake in adjacent bone invaded by the primary tumor. Only two patients, of the 18 patients without direct bone invasion, had increased radioactivity in the tumors (11.1%). In evaluation of the metastatic lesions, increased Ga-67 uptake was observed in 8 of 8 metastatic sites (100%). However, Tc-99m MDP could only detect 5 of 12 metastatic sites (41.7%), which were all diagnosed to be bone metastases. None of the extraskeletal metastasis could be detected by Tc-99m MDP imaging. Ga-67 scintigraphy appears to be a very useful tool in the evaluation of both primary and metastatic lesions of MFH and is assumed to be useful in the follow-up. However, it is emphasized that bone scintigraphy is useful only when the tumor invades the skeletal system and is of limited value in the evaluation of extraskeletal lesions.