Intramuscular spindle cell lipoma of the sternomastoid muscle – imaging and pathological appearances

Spindle cell lipoma (SCL) is a rare neoplasm occurring predominantly in male patients between the ages of 45 and 70 years. We present a case of SCL arising in the sternomastoid muscle of a 46 year old male patient, which was completely excised at surgery. (Only 4 cases of SCL have been described within skeletal muscle and SCL has not previously been reported within sternomastoid.) The histological and magnetic resonance (MR) imaging features of this lesion are described and the differential diagnosis is discussed, with particular reference to its potential confusion with liposarcoma.