Objective To analyze and summarize the clinical and ultrasonographic features, as well as the diagnostic and therapeutic experiences, of patients with primary thyroid lymphoma (PTL). Methods A total of 9 consecutive cases of PTL, confirmed by pathological biopsy and admitted to Shanghai Sixth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine from October 2022 to December 2024, were collected. A retrospective analysis was conducted on their clinical data, ultrasonographic characteristics, pathological diagnostic methods, and diagnosis and treatment process. Results Among the 9 patients (7 females, 2 males), the median age was 76 years (range: 39-88 years). All patients presented with progressively enlarging neck masses, six cases had obstructive symptoms, and eight cases were complicated with Hashimoto's thyroiditis (HT). Ultrasonography classified cases as: diffuse type (n=2, diffusely enlarged involved lobe with hypoechogenicity, internal linear echoes, and posterior acoustic enhancement), nodular type (n=3, solitary hypoechoic nodules), and mixed type (n=4, glandular enlargement with multifocal hypoechoic lesions). Regarding pathological diagnosis methods, 5 cases were confirmed by fine needle aspiration (FNA) combined with core needle biopsy (CNB), 2 cases were directly diagnosed by CNB, and 2 cases were diagnosed by surgical pathology. All patients initially received immunochemotherapy (R-CHOP/miniCHOP or Pola-R-miniCHP ± Glofit, 6-8 cycles). Three patients with incomplete remission received subsequent involved-site radiotherapy. Among 7 evaluable patients, 4 achieved complete remission (CR), 2 had partial remission (PR), and 1 died of progression after PR. Conclusions When elderly HT patients pre-sent with rapidly enlarged thyroid mass and obstructive symptoms over a short period, the possibility of PTL should be suspected. Characteristic ultrasonographic features include diffuse/nodular hypo-/marked hypoechoic lesions with internal linear hyperechoic strands, posterior acoustic enhancement, abundant vascularity, and absence of calcification. When PTL is clinically suspected, CNB cytology examination is recommended as the preferred method to improve diagnostic accuracy. Comprehensive treatment based on immunochemotherapy with or without radiotherapy can provide a favorable prognosis.