Sinonasal malignant lymphomas: a distinct clinicopathological category.

Sinonasal lymphomas represent a distinct subset of extranodal head and neck lymphomas. While sinonasal lymphomas are relatively rare in Western countries, in Asian populations they are the second most frequent group of extranodal lymphomas, after gastrointestinal lymphomas. With advances in immunohistochemistry, these lymphomas have been separated into B-cell, T-cell, and most recently into natural killer (NK) cell phenotypes. The B-cell phenotype is typically located in the paranasal sinuses and has a slight predominance in Western countries. The T/NK-cell phenotype is the most common in Asian and South American countries. These tumors are typically located in the nasal cavity and have an aggressive, angioinvasive growth pattern that often results in necrosis and bony erosion. Thus, sinonasal lymphomas have been included in the past with other destructive malignant and benign lesions under the descriptive and nonspecific name lethal midline granuloma. Patients are classically in the sixth to eighth decades, with a 2:1 male-to-female ratio. The prognosis is generally better than that of nodal-based lymphomas of similar histologic grade. Treatment is a combination of local irradiation and chemotherapy with an anthracycline-based regimen.