Callus formation of the tibial hallux sesamoid mimicking a bone tumor.

Sesamoid tumors of the hallux are rare, and their incidence and differential diagnosis have not been well described. We present a case with a bizarre callus formation of the medial sesamoid of the hallux that mimicked a bone tumor. After excision of the mass and related sesamoid, the patient remained asymptomatic during 3 years of follow-up.