MRI and PET-CT in the diagnosis and follow-up of a lymphoma case with multifocal peripheral nerve involvement.

Lymphoma of the peripheral nerve, particularly of the T-cell variety, is an extremely rare subtype of extra nodal lymphoma that has a variable response to current therapeutic regimens. Here, we present a patient with natural killer (NK)/T-cell lymphoma in remission who presented with a two-month history of right forearm swelling and paresthesia in the ulnar nerve distribution. Magnetic resonance imaging (MRI) showed an ulnar nerve mass identified as a nerve sheath tumor. Frozen section and postresection biopsies showed an Epstein-Barr virus-positive NK/T-cell lymphoma, nasal type. Consequently, the patient received chemotherapy following resection. Four months later, the patient developed a proximal leg mass, which was diagnosed as tibial nerve lymphoma. The patient was then treated with chemotherapy and follow-up was done by positron emission tomography-computed tomography (PET-CT). In conclusion, lymphoma should be considered in the differential diagnosis of a peripheral nerve mass. MRI is a useful imaging tool together with PET-CT, which plays a beneficial role in the follow-up of these patients on therapy as well as diagnosis of new lesions.