Large schwannoma in the ulnar nerve in axilla - A case report

Abstract

Introduction: Schwannomas are nerve sheath tumours which majority is benign. Only one case of solitary schwannoma in the ulnar branch of brachial plexus in the axilla is so far reported. Some are asymptomatic while others having pain and neurological disability. For diagnosis, imaging studies such as ultrasonography, computerized tomography, magnetic resonance imaging, electromyography and aid of electron microscopy and immunohistochemistry are used. Non-surgical treatment is appropriate for slow growing and asymptomatic tumours. Surgical treatment is aimed to prevent progressive neurological deficit. Damage to the parent nerve is a known complication.

Case report: A 44 year old female was investigated for a lump in her left axilla. Ultrasonography showed well defined hypoechoic solid mass, suspicious of an enlarged lymph node in the axilla with normal breasts. Tru-cut biopsy was compatible with histological appearance of schwannoma. A large (7.0x5.5x4.0cm3) well circumcised white mass of tissue arising at the origin of ulnar nerve deep in the left axilla was enucleated. Histologically lesion was compatible with a schwannoma with an intact capsule. Diffusely positive S-100 protein was demonstrated immunohistochemically and malignancy excluded. Post-operatively patient had ulnar nerve palsy confirmed by nerve conduction studies. Hand physiotherapy was offered and nerve function gradually improved.

Discussion: Benign schwannoma of the ulnar nerve is not a common condition encountered in general clinical practice, hence delay in diagnosis is of concern. MRI and histology is needed to diagnose schwannoma accurately and to exclude malignancy. Treatment is complete excision while preserving nerve function preferably under intra-operative electrophysiological guidance.