[Primary testicular NK/T cell lymphoma: a clinicopathologic analysis of six cases].

Objective: To evaluate the clinicopathological features, diagnosis and management of primary testicular NK/T cell lymphoma (NKTCL). Methods: Six cases of primary testicular NKTCL at Beijing Friendship Hospital, Capital Medical University from January 2007 to December 2016 were retrospectively analyzed for the morphology, immunephenotype and outcome, and relevant literature was reviewed. Results: The median age of patients at diagnosis was 45 years(range 32-65 years). All patients presented with testicular masses as initial symptoms (6/6), five cases (5/6) were on the right. The lesions were confined to the testis. All patients were classified as Ann Arbor stage Ⅰ but the tumors exhibited aggressive clinical behavior. Two patients died of the disease within two months, three (3/6) had clinical remission, and one (1/6) was lost to follow-up. Morphologically, the lymphoma cells showed a diffuse growth pattern that largely effaced the interstitial tissues, and surrounded seminiferous tubules in all cases. There was also a prominent angioinvasive pattern, with focal necrosis and karyorrhexis(4/6). Cytologically, the medium-sized neoplastic cells showed scanty to moderate amount of cytoplasm and irregular folded nuclei. The immunophenotype was similar to that of nasal NKTCL: the neoplastic cells were positive for cytoplasmic CD3, CD56, cytotoxic molecules and EBV-encoded small RNA, the loss of CD5 antigen was seen in all cases. Conclusions: Primary testicular NKTCL is extremely rare, highly aggressive and is associated with a poor prognosis. There is no unified standard of treatment. Thus, at the time of diagnosis of testicular lymphoma, NKTCL should be included in the differential diagnosis.