Schwannoma of the median nerve.

A schwannoma is a benign tumour of Schwann cells that presents as a palpable and painless mass on the volar aspect of the hand and wrist. A 44-year-old, right-handed woman, presented for a volar swelling of her right hand. On examination she had a non-pulsatile mass with no fluctuation at the radiopalmar aspect of the right hand, and a soft mass on the volar aspect of the right palm. There was no pain on palpation. An excisional biopsy specimen showed an encapsulated and extrafascicular tumour that originated in the median nerve fascicules. Histological examination showed a median nerve schwannoma measuring 4.0 x 1.5 x 1.2 cm. Differential diagnosis of hand tumours is divided into three categories: tumours of the soft tissue, bone, and skin. Schwannomas of the median nerve make up 0.1%-0.3% of all hand tumours. Symptoms are caused by an entrapment syndrome resulting from the growing tumour. Pain is the most common complaint of schwannomas distal to the wrist. Imaging studies include computed tomography (CT) and magnetic resonance imaging (MRI). It is difficult to differentiate schwanommas from neurofibromas solely on the basis of an MRI. Neurofibroma grows intraneurally and infiltrates the nerve; it has the potential to require resection of all or part of the nerve, leaving a consequent functional deficit. Tumours of the hand are diagnostically challenging and median nerve shwannomas are rare.