Imaging of Extra-nodal Head and Neck Lymphoma and its Mimics.

Extra-nodal head and neck lymphoma encompasses diverse histological subtypes and imaging appearances. Thus, it can be challenging to discriminate lymphoma from other lesions that may have similar radiological features. Herein, various lymphoma mimics will be reviewed in different anatomical locations in the head and neck including Waldeyer's ring, sinonasal tract, orbits, and salivary and thyroid glands, with reference to their clinical presentation, predisposing factors, and laboratory markers. These mimics encompass non-neoplastic (idiopathic orbital pseudotumor, granulomatosis with polyangiitis, IgG4-related disease and Rosai-Dorfman disease) and neoplastic (squamous cell carcinoma, NUT carcinoma, lymphoepithelial carcinoma) conditions. Red flags on imaging that should raise the suspicion for atypical lymphoma or potential mimics over typical lymphoma will be discussed. By the end of this review, radiologists should be able to differentiate lymphoma from its mimics in the head and neck, with the goal of improving imaging interpretation, reducing unnecessary biopsies, and providing the best patient management. Educational objectives.