Schwannoma of the extremities: comparison of MRI and pentavalent technetium-99m-dimercaptosuccinic acid and gallium-67-citrate scintigraphy.

The diagnostic value of MRI and scintigraphy was studied in patients with Schwannomas of the upper or lower extremities. MRI (T1- and T2-weighted imaging), pentavalent 99mTc-dimercaptosuccinic acid and 67Ga-citrate scintigraphy were performed in 11 patients with 12 histologically proven benign Schwannomas. All six tumors with a maximum diameter > or = 3 cm showed marked accumulation of pentavalent 99mTc-dimercaptosuccinic acid, whereas they showed no uptake of 67Ga-citrate. MRI detected all of the tumors, and the lesions had a signal intensity equal to or slightly less than that of skeletal muscle on T1-weighted images and hyperintense to that of subcutaneous fat on T2-weighted images. MRI was superior to detect small Schwannomas of the extremities. A positive 99mTc-dimercaptosuccinic acid scan and a negative 67Ga-citrate scan however is useful to distinguish sarcoma with myxoid change from Schwannoma.