Follicular lymphoma of the salivary gland: a clinicopathological and molecular study of six cases.

To clarify the clinicopathologic, immunohistologic, and genotypic features of follicular lymphoma arising from the salivary glands, we examined 20 cases of operatively resected primary salivary gland lymphoma and identified 6 such cases. There were 4 women and 2 men with ages ranging from 38 to 64 years (median 50 years). The tumor arose from the parotid gland in 4 cases and the submandibular gland in the remaining 2. Four patients were stage IE and 2 were stage IIE-1. The median follow-up period was 49 months and all patients were alive and well at the time of going to press. Histologically, 5 patients were follicular lymphoma grade 2, and 1 was grade 3. In all specimens in noninfiltrating salivary gland tissue, there was periductal lymphocytic infiltration near the lymphoma. Moreover, myoepithelial sialoadenitis was noted in 2 lesions. An immunohistochemical study revealed all 6 cases were CD10+, CD79a+, bcl-6+, CD3-, CD5-, CD21-, CD23-, and CyclinD1-. The tumor cells expressed bcl-2 in 3 cases and p53 oncoprotein in 4 cases. Two cases revealed clonal bands with polymerase chain reaction (PCR) assay for the immunoglobulin heavy (IgH) gene. The bcl-2/IgH translocation at the major breakpoint region was detected in 1 case (16%). We found a relatively high incidence of follicular lymphomas (30%) in salivary gland lymphomas. Among the mucosa-associated lymphoid tissue (MALT) system, follicular lymphomas appeared to occur frequently in the salivary glands as well as the duodenum and skin. Moreover, follicular lymphoma arising from the salivary glands appeared to have some of the characteristics of MALT-type lymphoma including indolent prognosis, presence of myoepithelial sialoadenitis, and rarity of the BCL-2 gene rearrangement.