Tenosynovial Giant Cell Tumor (TGCT), Localized Type

Background:

• Rare, benign tumor involves joint synovium, bursa, and tendon sheath, which rarely undergoes malignant transformation
• When occurring in the spine, >50% occur in the cervical spine, one-third of which occur in the upper cervical spine (C1–C2). These are usually centered in the facet joints, growing diffusely outside the joint and invading near vertebrae.

Clinical Presentation:

• Incidental finding; otherwise, can present with neurologic symptoms (pain, numbness, weakness)

Key Diagnostic Features:

• CT findings: soft tissue mass; may have cortical erosions with sclerotic margin
• MRI findings:
  • Lobulated mass, T1/T2 intermediate/hypointense; may have hypointense fibrous septations
  • Usually shows intense enhancement
  • Blooming on gradient-echo sequences indicating hemosiderin deposits

Differential Diagnoses:

• Metastasis: irregular margins with cortical destruction, T2 hyperintense/heterogeneous
• Multiple myeloma/Plasmacytoma: cortical destruction +/- pathologic fracture, T2 hyperintense, usually restricted diffusion
• Chordoma: centrally located, marked T2 hyperintense, heterogeneous enhancement
• Lymphoma: commonly irregular margins, permeative bone destruction, T2 hyperintense
• Osteoblastoma: expansile bone tumor, predominantly lytic, T1/T2 hypointense foci corresponding to calcifications/osteoid matrix
• Synovial sarcoma: more heterogeneous T2 signal due to necrosis and dystrophic calcifications or fibrotic bands, more aggressive cortical destruction

Treatment:

• Gross total resection