Synonyms

• Localised TGCT
• giant cell tumour of tendon sheath
• nodular tenosynovitis
• PVNS

Category

Soft tissue

Behaviour

Benign

Gender

Female

Tissue of Origin

Synovial/tenosynovial tissue

Epidemiology

• Most common tumour of tendon sheath
• Peak incidence in 3rd–5th decades
• CSF1 overexpression drives tumour proliferation

Clinical Features

• Painless firm nodule on palmar surface of finger or hand
• Slowly growing, may cause pressure erosion of adjacent Bone
• Non-tender, lobulated, well-defined
• Restricted tendon gliding

Location

• Fingers (most common - palmar surface)
• Hand and wrist
• Ankle and foot
• Knee (rarer - localised form)

Imaging

• Well-defined lobulated hypointense mass on MRI (haemosiderin)
• Bone erosion on X-ray in 10%
• Low signal on both T1 and T2 (haemosiderin) - characteristic
• Ultrasound: solid hypoechoic mass adjacent to tendon

Pathology

• Synovial-type cells, osteoclast-type giant cells, foam cells, and haemosiderin
• CSF1 overexpression - drives tumour proliferation and macrophage recruitment
• Lobulated with Fibrous septae
• CSF1R mutation or translocation in a subset of cells

Genetics

• CSF1-COL6A3 translocation (2p13; 1p13) in subset of neoplastic cells
• CSF1 overexpression recruits non-neoplastic macrophages (tumour microenvironment)
• Clonal neoplasm despite reactive appearance

Treatment

• Surgical excision - marginal excision curative in most
• Complete excision of all lobules reduces recurrence risk
• Pexidartinib (CSF1R inhibitor): FDA-approved for symptomatic TGCT not amenable to surgery

Prognosis

• Local recurrence 10–20% after marginal excision
• No Malignant potential for localised type
• Pexidartinib achieves durable responses in unresectable cases

Key Points

• Most common tumour of tendon sheath - palmar surface of digits is classic location
• Low signal on T1 and T2 MRI due to haemosiderin is characteristic
• Pexidartinib (CSF1R inhibitor) is FDA-approved for symptomatic unresectable TGCT
• Complete excision of all lobules is key to reducing recurrence

Workup - Blood Tests

No routine blood tests required

Workup - Local Imaging

• Ultrasound or MRI tendon sheath - well-defined hypoechoic/hypointense nodule; haemosiderin (Low T1/T2)
• Plain radiograph - assess for Bone erosion

Workup - Biopsy

Biopsy rarely required if imaging characteristic

Workup - Staging

None required

Follow-up Summary

• Benign soft tissue tumour (localised TGCT) - Follow-up to detect local recurrence
• Post-op visit at 6 weeks; USS or MRI of tendon sheath at 3 months as new baseline
• Year 1: Single review at 6 months - clinical exam + USS
• Year 2: Annual review; USS if symptomatic
• Discharge at 2 years if asymptomatic and no clinical recurrence
• Recurrence (10–20%): re-excision; if multiple recurrences consider pexidartinib referral
• No systemic metastatic surveillance required