Definition
A keratin filled cyst lined by stratified squamous epithelium. It forms when epidermis is implanted into deeper tissue by penetrating trauma.
Epidemiology
- Third commonest hand tumour after ganglion and giant cell tumour of tendon sheath
- Men more than women
- Manual workers with a history of penetrating injury
Pathology
- Wall of keratinising squamous epithelium with laminated keratin contents
- Soft tissue type in the palm and fingertip pulp
- Intraosseous type in the distal phalanx, sometimes after nail bed injury or amputation
Clinical Features
- Firm painless mobile nodule on the volar finger or palm
- Slow growth over months to years
- Intraosseous lesions cause a painful swollen or clubbed fingertip
- Nail deformity with distal phalanx lesions
Investigations
- Radiograph shows a well defined lytic lesion with a sclerotic rim in the intraosseous type
- Ultrasound shows a well defined hypoechoic lesion with internal echoes
- Histology confirms the diagnosis
Differential Diagnosis
- Ganglion of the wrist and hand
- Giant cell tumour of tendon sheath
- Enchondroma
- Glomus tumour
- Giant cell reparative granuloma
Management
- Marginal excision. Complete removal with the cyst wall intact
- Curettage and bone graft. Intraosseous lesions of the distal phalanx
- Terminalisation. Extensive distal phalanx destruction
Complications
- Recurrence after rupture or incomplete excision
- Rare malignant change to squamous cell carcinoma
- Digital nerve injury during excision
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 19 October 2026.