Tenosynovial giant cell tumors of digits: MRI differentiation between localized types and diffuse types with pathology correlation

Objective To compare the MRI findings between the localized- and diffuse-type tenosynovial giant cell tumors (TSGCTs) of digits with pathology correlation. Methods Twenty-eight patients with newly diagnosed TSGCTs of digits (22 localized and 6 diffuse types) who underwent preoperative MRI and surgical excision were included from Jan. 2015 to September 2021. MRI findings regarding nodularity, margins, morphology of hypointensity with pathology correlation, and disease extent (bone erosion, articular involvement, muscle involvement, tendon destruction, and neurovascular encasement) were assessed. Results Diffuse type was significantly larger ( P = 0.006), more multinodular on both MRI and pathology ( P = 0.038, both) with significant agreement, and infiltrative on both MRI and pathology ( P < 0.001, both) with substantial agreement, and showed central granular on MRI and strong hemosiderin deposition on pathology ( P = 0.022 and P = 0.021) with moderate agreement than localized type. Localized type showed significantly more frequent peripheral capsules on both MRI and pathology ( P < 0.001, both) with moderate agreement than diffuse type. However, the septum on both MRI and pathology showed no statistically significant difference between the two groups ( P = 0.529 and P = 0.372) without significant agreement. The disease extent was more severe in the diffuse type than the localized type regarding articular involvement ( P < 0.001), muscle involvement ( P < 0.001), and tendon destruction ( P = 0.010). No statistically significant differences were found between the two groups regarding bone erosion ( P = 0.196) or neurovascular bundle encasement ( P = 0.165). Conclusions Diffuse-type TSGCTs of digits presented as locally aggressive lesions with larger, multinodular, infiltrative masses exhibiting stronger hemosiderin deposition and more severe disease extents of articular, muscle, and tendon involvement than the localized type.