Intramuscular schwannoma of the musculocutaneous nerve: An uncommon clinical presentation.

A schwannoma is a benign peripheral nerve sheath tumor composed exclusively of Schwann cells. A major-nerve schwannoma with an intramuscular location is an extremely rare condition. We present a rare case of intramuscular schwannoma originating from the musculocutaneous nerve in a 71-year-old female. The patient presented with a 7-month history of a slowly growing, painless mass in the medial aspect of the proximal upper arm. Magnetic resonance imaging revealed an oval-shaped intramuscular soft tissue mass with iso-signal intensity relative to skeletal muscle on T1-weighted images and high signal intensity on T2-weighted images. A rim of fat surrounding the mass, suggesting the split-fat sign, was also observed. The tumor was completely enucleated using an intracapsular technique. Histological examination confirmed the diagnosis of schwannoma consisting of Antoni A and B areas. There was no immediate neurological deficit following surgery. The patient had no evidence of local recurrence and no neurological deficit at final follow-up. To the best of our knowledge, this is the first report of musculocutaneous nerve schwannoma within the coracobrachialis muscle.