Presentation
Increasing focal swelling of little finger. Minimal pain.
Patient Data
Focal soft-tissue swelling at the radial volar aspect of the right 5th finger at the level of the proximal interphalangeal joint. There is no soft-tissue calcification in association, but there is relatively well-defined erosion of the volar aspect neck of the proximal phalanx and base of the middle phalanx.
Lobulated predominantly hypoechoic lesion surrounding the flexor tendon at the level of the 5th proximal interphalangeal joint. The lesion has solid components with vascularity demonstrated and causes juxta-articular erosions at the volar aspect of proximal and middle phalanges corresponding to the plain radiographic appearance.
Bony erosion (chronic pressure remodelling) due to the soft-tissue mass (red arrows).
Case Discussion
Soft-tissue mass arising from the flexor tendon sheath at the level of the 5th proximal interphalangeal joint and inducing bony scalloping. The major differential diagnosis would be between giant cell tumour of tendon sheath and synovial sarcoma. Subsequent MRI (not currently available for upload) confirmed the findings and revealed haemosiderin staining of the mass most consistent with giant cell tumour of tendon sheath.