Primary CD56-positive NK/T-cell lymphoma of median nerve: a case report.

Primary extranodal lymphomas of the central nervous system constitute 2% of all malignant lymphomas. The involvement of the peripheral nervous system is very rare. A solitary primary CD56-positive NK/T-cell lymphoma of the median nerve is described in a 70-year-old woman. On physical examination, a rubbery hard mass measuring 2.0 cm in diameter was palpated on the volar aspect of second to third finger of left hand. Excisional biopsy was performed. Under the fascia, a large fusiform tumor of the median nerve encapsulated with the epineurium was noted. Microscopically, the enlarged nerve showed extensive infiltration of atypical lymphoid cells. The lymphoid elements had abundant pale cytoplasm and large vesicular nuclei with peripheral prominent nuclei. The cells strongly expressed T-cell marker (UCHL-1) and natural killer cell marker (CD56). Gene rearrangement study showed rearrangement of T cell receptor (TCR-gamma).