PurposePrimary thyroid lymphoma (PTL) is a rare disease and it has been investigated in a limited number of studies. The present multicenter study evaluated the clinical features and treatment outcomes of PTL.MethodsThe medical records of patients diagnosed with PTL between 2000 and 2013 in three centers were retrospectively reviewed.ResultsThe study included 11 men and 27 women with a median age of 63.3 years (range, 42-83 years). The median follow-up was 56.0 months (range, 3-156 months). Of the 38 patients included, 16 had mucosa-associated lymphoid tissue (MALT) lymphoma, six had mixed MALT and diffuse large B-cell lymphoma (DLBCL), and 16 had DLBCL. Thirty-five patients (92.1%) had early stage (stage I/II) disease. Of the 16 MALT lymphoma patients, 14 were treated by surgery, and radiotherapy (RT) or chemotherapy was combined in five patients. Two patients received RT or chemotherapy alone. Of the six mixed MALT and DLBCL patients, three underwent surgery with chemotherapy and three underwent chemotherapy alone, RT alone, or surgery with RT. All of the 16 DLBCL patients received chemotherapy, and surgery and RT was combined in 4 and 1 patients, respectively. The 5-year survival was 100% for MALT lymphoma (7 of 7) and mixed MALT and DLBCL patients (5 of 5) and 87.5% for DLBCL patients (7 of 8).ConclusionEarly stage PTL has an excellent prognosis when managed by single or combined treatment modalities. Clinicians should consider PTL in patients with underlying Hashimoto's thyroiditis presenting with an enlarging thyroid mass.