Sinonasal Lymphoma: Extranodal Natural Killer/T-Cell Lymphoma and Its Differential Diagnosis

Abstract Lymphoma is the second most common malignancy in the nasal tract and paranasal sinuses after squamous cell carcinoma (Acta Oncol 1997;36:45–50). Sinonasal lymphoma is the most common hematolymphoid lesion at the site, accounting for approximately 1% of all lymphomas (Virchows Arch A Pathol Anat Histopathol 1989;414:399–405). These neoplasms are diverse, including B cell, T cell, and natural killer cell differentiation. This group of lymphomas includes chronic and aggressive entities, some with clearly defined etiologies and associations including Epstein-Barr virus, HIV, and human T-cell leukemia virus infections, with variable differentiation and distinctive growth patterns. In this report, we will review the most prevalent entities with a focus on extranodal natural killer/T-cell lymphoma. A sinonasal lymphoma differential diagnosis is provided with review of the epidemiologic, histomorphologic, and immunophenotypic characteristics and discuss diagnostic pitfalls. The discussion is accompanied by representative micrographs, with an explanation of the particular features of each diagnosis. Lastly, we will briefly discuss important clinical characteristics.