T2-star (T2*)-weighted magnetic resonance imaging of tenosynovial giant cell tumors.

Purpose: Tenosynovial giant cell tumors (TSGCTs) are benign but aggressive lesions, and the treatment is resection. A low to intermediate signal intensity on both T1- and T2-weighted images of magnetic resonance imaging (MRI) is characteristic, which is similar to the signal intensity of muscle, and therefore can be challenging for lesion detection. T2-star (T2*)-weighted MR images reflect paramagnetic deoxyhemoglobin, methemoglobin, or hemosiderin. Methods: In 23 TSGCT patients (6 male and 17 females), the T2*MRI findings were analyzed. The tumor locations involved 10 large joints including nine knees and one ankle, 10 small joints including six fingers and four toes, as well as three wrists/hands. Results: Ten diffuse and 13 localized tumors were predominantly located in the large joints and small joints, respectively. The T2*-weighted images indicated three signal patterns of low, iso and high signal intensity compared to muscle. Low-, iso- and high-signal intensities were seen in 22 (96 %), 23 (100 %) and 12 (52 %) of the locations, respectively. To distinguish TSGCTs from the surrounding tissue, the low intensity T2*-weighted images and low to intermediate intensity T1-weighted images when compared to muscle and fluid, respectively were useful for the large joints. Low to intermediate intensity on T1- or T2-weighted images was useful to distinguish TSGCTs from subcutaneous tissue in the small joints. Conclusions: MRI using T2*-, as well as T1- and T2-weighted images, may be useful to detect lesions and assess the extent of TSGCTs in a tissue-specific manner, which is important for surgical planning.