An unusual cause of facial swelling: primary extranodal non-Hodgkin lymphoma of the masseter muscle.

Nearly 25% of non-Hodgkin lymphomas (NHLs) arise in extranodal locations. The involvement of soft tissue by NHL is uncommon. Primary extranodal NHL of the skeletal muscle is even rarer. The authors report a 49-year-old man with a 3-month history of progressive asymmetry of the face caused by swelling in the right cheek with paresthesia and burning. He underwent an excisional biopsy of the lesion. Histologic examination, immunohistochemistry and cytogenetic analysis were performed. The final diagnosis was primary large B-cell NHL of the masseter muscle, stage IEA. Rituximab-cyclophosphamide, epirubicin, vincristine and prednisone regimen was started. Restaging procedures after immunopolychemotherapy showed no evidence of disease. No relapse has occurred during a follow-up of 72 months. Although primary muscle lymphoma represents a rare entity, it can involve every muscle. Thus, when patients present with cheek swelling, physicians should always consider the possibility of lymphoma. The authors also reviewed the published literature concerning primary muscle lymphoma.