Primary thyroid T cell lymphoproliferative disorder with a 10-year history of neck mass: a case report and literature review

Thyroid lymphoproliferative disorder is known to be associated with Hashimoto thyroiditis. The major histological types of thyroid lymphoproliferative disorders are malignant lymphoma, such as diffuse large B cell lymphoma, extranodal marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT), and follicular lymphoma. All of these are B cell lymphomas; however, T cell lymphoproliferative disorders represent only a minority of cases. Since T cell lymphoproliferative disorder rarely develops and T cell lymphoma is a heterogeneous entity, it is difficult to concisely summarize this complex topic. Here, we present a case of primary thyroid T cell lymphoproliferative disorder reminiscent of indolent T cell lymphoproliferative disorder of the gastrointestinal tract: the pathological findings from this case also were similar to those of MALT lymphoma such as small lymphoid cells, lymphoepithelial lesions, and a low Ki-67 labeling index. T cell lymphoproliferative disorders with these pathological features have been reported in the thyroid gland, lymph nodes, palate, spleen, and gastrointestinal tract. Furthermore, we reviewed and summarized the studies on thyroid T cell lymphoproliferative disorders and compared the cases and their clinicopathological characteristics.