An unusual case of an intramuscular lipoma of the pectoralis major muscle simulating a malignant breast mass.

INTRODUCTION Intramuscular lipomas of the pectoralis major muscle are rare and may mimic malignant breast tumours. CLINICAL PICTURE A 58-year-old Chinese woman presented with a 2- year history of an enlarging left breast mass. Clinical examination revealed a palpable hard mass in the left breast. TREATMENT Standard mammographic views revealed a radiolucent mass deep in the left pectoralis major muscle. The mass was homogeneously hypoechoic with smooth margins on ultrasound. OUTCOME Surgical excision of the mass was performed. Histological diagnosis was an intramuscular lipoma of the left pectoralis major muscle. CONCLUSIONS Recognition of the radiolucent density and submammary location of a pectoralis major muscle lipoma is important as it allows the correct diagnosis to be made.