Primary lymphoma of the medial cutaneous nerve of the forearm: the first case in a pure sensory nerve of the upper limb.

Primary lymphoma of the peripheral nerve is very rare and occurs most frequently in sciatic nerves. We describe the first patient reported in literature with a primary lymphoma in a pure sensory peripheral nerve of the upper limb. A woman in her 40s, with painful swelling and dysaesthesias in her left forearm in the past 3 months, was presented at our unit. Clinical MRI and ultrasound findings revealed a lesion that showed signs of a peripheral nerve sheath tumour. After complete excision, morpho-pathological evaluation revealed a primary B-cell lymphoma. The patient underwent radiotherapy and at the last follow-up there were no signs of residual pathology. Peripheral neuropathy may be caused by a lymphoma involving the nerve. Hand surgeons have to distinguish primary lymphoma of the peripheral nerves from schwannoma for their different clinical behaviour.