Atypical tenosynovial giant cell tumor of the extensor hallucis longus tendon.

We present a case of atypical giant cell tumor of the tendon sheath originating from the extensor hallucis longus tendon. The tumor contained multiple nodules and overlay the tendon 16 cm. Magnetic resonance imaging was the most useful preoperative investigation and showed the characteristic appearance of giant cell tumor of the tendon sheath, thus allowing local excision to be planned and executed. We discuss how local recurrence of this tumor could be prevented.