Parotid gland mucosa associated lymphomas and their cytologic mimics

Although the parotid is a target for myoepithelial sialadenitis and lymphomas of mucosa associated lymphoid tissue (MALTomas), MALTomas are rare and have not been well characterized in the cytology literature. We examine fine needle aspiration biopsies from 19 lymphoid lesions of the parotid gland with particular emphasis on MALTomas and their cytologic look-a-likes. Purely on cytology it is difficult to distinguish with certainty a MALToma from a late-phase reactive lymph node. Both conditions were predominantly composed of small mature appearing lymphocytes and both occasionally had larger lymphocytes with tingible body macrophages. By contrast, the diagnosis of non-MALT lymphoma was usually straight forward, as they had overt cytologic atypia. In applying fine needle aspiration biopsy to large or persistent lymphoid lesions of extra-nodal sites like the parotid gland, we recommend the liberal use of flow cytometric analysis to distinguish between reactive lymph nodes and MALToma and to more precisely classify non-MALT lymphomas.