Abstract: Objective: To investigate the clinicopathologic features and immunophenotype of Hashimoto's thyroiditis(HT) complicated with primary thyroid lymphoma(PTL),and explore the diagnosis,differential diagnosis,treatment and prognosis of PTL.Methods: Four cases with HT complicated with PTL were collected according to the WHO classification standard of lymphomas(2008).The clinicopathologic features and immunophenotype of 4 cases were analyzed,and the patients were followed up.Results: Among 4 PTL cases,male in 1 case and female in 3 cases were found,and the age of the patients was from 56 to 62 years old.The unilateral painless thyroid masses was the primary symptom.The medium or large neoplastic lymphocyte infiltration,remaining thyroid gland,glandular atrophy and lymphoepithelial lesion were found under light microscope.Conclusions: The PTL is rare,which is closely related to the occurrence of HT.The immunohistochemical label can help the accurate diagnosis.The surgery combined with chemotherapy and/or radiotherapy is the suitable treatment.