Among 42 133 cases of diffuse large B-cell lymphoma (DLBCL) registered at the Surveillance, Epidemiology and End Results (SEER) database between 2001 and 2009, we found 487 cases (1.2%) of thyroid DLBCL. Patients were predominantly female, older and less likely to present with advanced disease than their counterparts with DLBCL of another extranodal or nodal site. Survival was superior for patients with thyroid DLBCL, even when adjusted for patient characteristics and stage. Among the 411 patients with stage I/II disease (84%), 351 had available information regarding surgical resection and radiation and at least 4 months of follow-up. Risk of death was higher for subjects who did not receive resection or radiation (hazard ratio = 2.63, 95% confidence interval 1.43-4.85), but not affected by the omission of one of these therapeutic modalities. The use of surgery or radiation may add to systemic treatment and improve survival of patients with stages I/II thyroid DLBCL.