Giant cell tumour of the flexor tendon sheath of the foot.

Giant cell tumour of tendon sheath (GCTTS) is a benign, soft-tissue tumour arising from synovial cells of tendon sheaths. Because of the high incidence of recurrence, radical surgical excision is the treatment of choice. Presented here is a rare case of this lesion originating from flexor tendon sheaths of the foot. A 40-year-old Russian white female presented to the clinic with a slightly painful soft tissue mass in her right foot along the medial aspect of her ankle. She gave a one-year history of the mass and was concerned about increasing size, pain, and plantar numbness as well as limitation in her movements to some extent. Interpretation of the magnetic resonance imaging failed to include giant cell tumours in the preoperative differential diagnosis. Considering the proximity of the tumour to important anatomic structures, less radical but grossly complete excision was employed, followed by appropriate periodic re-evaluation. Pedal involvement of GCTTS is rare with a reported predilection for dorsal and lateral localisations around the ankle. Our case presents an unusual occurrence of this tumour with medial localisation of the lesion in the foot, extending through the tarsal tunnel.