Objective:To explore the diagnosis and treatment strategies of multiple primary malignancies(MPM).Methods:The medical records and the process of diagnosis and treatment of a patient with heterochronous double primary cancer were retrospectively analyzed,and the treatment strategy was discussed by multi-disciplinary team(MDT).Results:A female patient with heterochronous double primary cancer was reported.The first primary tumor was gastric cancer and the second primary tumor was lung cancer.The first primary tumor was diagnosed at 67 years of age,and the interval between the first primary tumor and second primary tumor was 13 months.Pleural metastasis and pelvic metastasis occurred during the follow-up.Pleural metastasis originated from lung cancer,and pelvic metastasis was considered as gastric cancer implantation.Tumor MDT discussion was conducted at each stage of diagnosis and treatment,and the histopathological diagnosis was confirmed by puncture biopsy or surgical resection.The patient received systemic therapy combined with local treatment for metastases of different tumors and had a longer overall survival(67 months).Side effects were tolerable,and the quality of life was satisfactory throughout the treatment period.Conclusion:For patients with MPM,it is necessary to actively carry out MDT discussion,clarify the histopathological diagnosis,evaluate the clinicopathological and metastatic characteristics,and implement active and effective treatment.