Primary non-Hodgkin's lymphoma of the salivary gland: a spectrum of lymphoepithelial sialadenitis, low-grade B-cell lymphoma of mucosa-associated lymphoid tissue with transformation to high-grade lymphoma.

Lymphoid infiltrates of the salivary gland can be either reactive or neoplastic. The reactive lesion, lymphoepithelial sialadenitis (LESA) may be associated with Sjogren's syndrome (SS) or may occur as an isolated salivary gland enlargement. Patients with LESA/SS have a particularly high risk of subsequently developing lymphoma, which is a low-grade mucosa-associated lymphoid tissue (MALT) type lymphoma of the salivary gland. We document a rare case of primary non-Hodgkin's lymphoma of the parotid gland arising in the background of LESA and with a rare example of transformation from low grade to high-grade B cell lymphoma of MALT type.