Lymphoid lesions of the head and neck: a model of lymphocyte homing and lymphomagenesis.

Lymphoid lesions of the head and neck mainly affect the nasopharynx, nasal and paranasal sinuses, and salivary glands. These three compartments each are affected by a different spectrum of lymphoid malignancies and can serve as model for mechanisms of lymphomagenesis. The type of lymphoma seen reflects the underlying biology and function of the particular site involved. The nasopharynx and Waldeyer's ring are functionally similar to the mucosal associated lymphoid tissue (MALT) of the gastrointestinal tract and are most commonly affected by B-cell lymphomas, with mantle cell lymphoma being a relatively frequent subtype. The most prevalent lymphoid lesion of the salivary gland is lymphoepithelial sialadenitis, associated with Sjögren's syndrome. Lymphoepithelial sialadenitis is a condition in which MALT is acquired in a site not normally containing lymphoid tissue. Patients with Sjögren's syndrome are at increased risk to develop B-cell lymphomas, most commonly MALT lymphomas. The nasal and paranasal sinuses are the prototypical site for the development of extranodal natural killer (NK) /T-cell lymphoma, nasal type. This condition must be distinguished from other conditions causing the clinical picture of lethal midline granuloma, including Wegener's granulomatosis and infectious disorders. Lymphomatoid granulomatosis is common in the lung but is rarely seen in the midline facial structures.