AbstractThis paper describes the course of a patient with treated non-Hodgkin's lymphoma, which originally presented as a large nasopharyngeal mass. The tumor, though irradiated, recurred on two separate occasions in the right and left inguinal regions. At the time of tumor recurrence, markers were present which have been associated with past or recurrent Epstein-Barr virus (EBV) infection, namely, antibodies to the EBV viral capsid antigen (VCA) and the Epstein-Barr nuclear antigen (EBNA). EBNA was detected in approximately 10% of the neoplastic cells. An unusual immunoglobulin heavy and light chain switch within the tumor cells of the two separate inguinal node tumor recurrences was also observed. Whether EBV plays a role in the pathogenesis of lyphomas remains unclear.