Pathology of Lymphoma of the Thyroid

The thyroid may be involved secondarily by lymphoma from other sites in the body or by leukemic infiltrates (). Most primary thyroidal lymphomas are B-cell types, but both Hodgkin’s lymphoma (,) and T-cell lymphoma () may occur. Gross examination reveals homogeneous, pale, and firm tissue that has replaced the thyroid irregularly. If advanced autoimmune thyroiditis is also present, the lymphoma probably cannot be distinguished from the inflammatory infiltrate without histologic examination. Microscopically, the regions of autoimmune thyroiditis reveal either the usual benign lymphoplasmacytic infiltrates or the common alterations of the follicular epithelial cells (e.g., oxyphilic cell metaplasia).