Simple Bone Cyst (Benign Osteolytic Lesion) of 1st Metacarpal: A Rare Case Report

INTRODUCTION: A benign cystic lesion, the simple bone cyst (unicameral/essential bone cyst), it may be found in any long bone (most commonly found in femur and proximal humerus), usually in immature skeletal persons. Metacarpal simple bone cyst is an exceedingly rare occurrence and few treatment options have been described for the same. CASE REPORT: A 42-year-old manual laborer male (right hand dominant) came with history of trivial trauma to right hand thumb with hammer. He complained of mild swelling and pain since trauma. On imaging the right hand, an expansive lytic lesion was seen in the metaphyseo-diahyseal region of the first metacarpal. There was thinning of the cortex with break in cortex visible at mid diaphyseal region. There was absence of any soft-tissue involvement or periosteal reaction. Magnetic resonance imaging reported a T2 hyperintense and T1 isointense benign osteolytic lesion with pathological fracture. On aspiration, a reddish tinged fluid was found. A closed fixation was performed with the help of an intramedullary k-wire. CONCLUSION: Simple bone cyst, although rare in metacarpal bone, is an important differential diagnosis in cases with cystic lesion. Simple bone cyst, although a benign lesion, can cause extensive involvement of the metacarpal bones and destroy the entire diaphysis. It requires adequate treatment which is simple and effective.