Primary Diffuse Large B-Cell Lymphoma of the Frontal Sinus

A 73-year-old male presented with 6 months of right upper eyelid swelling and 3 weeks of progressive binocular diplopia. Examination was notable for right eye vision of 20/70, near-complete motility restriction, proptosis of 4 mm, complete ptosis, periorbital edema, and conjunctival injection (Fig. 1A); slip lamp and dilated examination were otherwise normal. CT demonstrated a large, homogenous, expansile mass extending from the right frontal sinus into the superior extraconal orbit. He was scheduled for surgery and placed on a preoperative prednisone taper. In the intervening month, he experienced rapid progression of disease, with severe periorbital edema and hemorrhagic chemosis (Fig. 1B). He underwent right anterior orbitotomy and frontal sinus exploration, total ethmoidectomy, and maxillary antrostomy. Orbital exploration revealed a firm, grey-tan-colored tumor invading the superior orbit (Fig. 1C). Histopathology revealed CD5 positive diffuse large B-cell lymphoma with MYC gene rearrangement. Staging work-up, including MRI (Fig. 2, top), revealed an interval increase in lesion size, with encasement of the right superior, medial, and lateral rectus muscles, superior oblique muscle, and optic nerve. He was diagnosed with stage IE diffuse large B-cell lymphoma of the frontal sinus and right orbit. He completed 3 cycles of rituximab, cyclophosphamide, hydroxydaunorubicin, oncovin, prednisone and consolidative radiotherapy. Follow-up nasal endoscopy, positron emission tomography, and MRI (Fig. 2, bottom) showed complete metabolic response. Primary frontal sinus lymphoma is a rare entity, typically manifesting with mass effect or cranial nerve palsy. It may mimic benign lesions, such as mucoceles, on imaging. Timely recognition and multidisciplinary management are crucial to reduce associated morbidity.

FIG. 1.: From initial presentation (A) to day of surgery (B), the patient experienced rapid progression of disease, with severe periorbital edema and hemorrhagic chemosis. Orbital exploration (C) revealed a firm, grey-tan-colored tumor invading the superior orbit.

FIG. 2.: Pre-chemoradiation, magnetic resonance imaging (top) showed a large, expansile mass extending from the right frontal sinus into the superior extraconal space, with encasement of multiple extraocular muscles and the optic nerve. Post-treatment imaging (bottom) demonstrated complete metabolic response.