Pattern recognition in the differential diagnosis of salivary lymphoepithelial lesions

The prototype of a salivary lymphoepithelial lesion is the autoimmune disease Sjögren's syndrome with the characteristic lymphoepithelial duct lesions (LEL). The distinction of Sjögren's syndrome from cases with initial transformation into associated marginal zone B-cell lymphoma (MALT type) can be very challenging, whereby the presence of small "halos" can lead to over-diagnosis. The HIV-associated cystic lymphoepithelial lesion can be histologically almost identical to Sjögren's syndrome and often needs clinical correlation. The sporadic lymphoepithelial cyst of the parotid gland is a frequent finding and has no clinical consequence; however, this entity needs to be identified and distinguished from the above-mentioned entities. The most frequent diagnosis in resected submandibular glands is chronic-fibrosing sialadenitis, so-called Küttner's tumour. Altogether, there is a wide spectrum of lymphoepithelial interaction in the area of salivary glands, including biphasic lymphoepithelial tumours with an obligate lymphoid component, epithelial tumours with facultative tumour-associated lymphoid proliferation, and different processes of intraparotid lymph nodes. The immunohistological reaction for pan-keratin can be very helpful for a thorough pattern analysis of the different lymphoepithelial lesions. The relative frequency of the lesions in different salivary glands can also be diagnostically helpful.