Abstract: The causes of cervical swollen lymph nodes are complex, mainly including lymph node matastasis, lymphoma, lymph node tuberculosis and other factors. The authors reported a case of diffuse large B-cell lymphoma (DLBCL) with cervical lymph node metastases in papillary thyroid carcinoma (PTC), and analyzes the characteristics of the disease in combination with the patient′s clinical symptoms, histopathological examination results, ¹⁸F-fluorodeoxyglucose (FDG) PET/CT imaging, and therapeutic process, etc, aiming at raising clinicians′ awareness of the ¹⁸F-FDG PET/CT imaging of DLBCL with cervical lymph node metastases in PTC and reducing the misdiagnosis rate of this disease.