Primary diffuse large B-cell lymphoma of the frontal sinus: A case report and literature review.

Diffuse large B-cell lymphoma arising as a primary tumor in the frontal sinus is very rare. Moreover, it is often difficult to diagnose frontal sinus lesions. A 67-year-old Japanese man initially presented with diplopia and a swollen left upper eyelid. Diffusion-weighted magnetic resonance imaging suggested a malignant lymphoma of the frontal sinus, and subsequent extensive examination revealed diffuse large B-cell lymphoma of the frontal sinus with left orbital invasion. Six courses of combined immunodirected chemotherapy were administered. The patient is tumor-free owing to the accurate diagnosis of lymphoma at an early stage.