Primary thyroid lymphoma: mucosa associated lymphoid tissue lymphoma case -

Primary thyroid lymphomas are lymphomas which are localized only to thyroid gland or thyroid gland and surrounding lymph nodes. Frequently these are mucosa associated lymphoid tissue (MALT) lymphomas with B cell origin. Our case is a 78-year-old female patient who admitted with a neck mass and had been operated with the suspicion of malignancy. Histopathological examination revealed diffuse proliferation of atypical lymphoid cells that consists of small to medium sized cells, with irregular nuclear contours, some of which resemble centrocytes. Immunohistochemical staining was positive for CD20, CD79alpha, CD43, and lambda while negative for CD3, CD30, CD15, bcl-2, bcl-6, CD68, CD138, CD5, and CD10. With these finding, the case was considered as “primary thyroid MALT lymphoma”. Thyroid MALT lymphomas are characterized with the presence of atypical lymphocytes that originate from the marginal zones of lymhoid follicles. Immunohistochemically, while these lymphomas express the B cell associated antibodies (CD20, CD22, CD79a), conversely CD5, CD10, and CD3 expressions are not seen.