Clinically, it has been observed that after consolidation chemotherapy following normal HCG, most patients with gestational trophoblastic tumors have disappeared from their lung lesions, but some patients still have persistent lung imaging lesions. Are there still active tumor cells inside these persistent lesions? Is it a high risk factor for disease recurrence? Some studies suggest that the persistence of lung imaging lesions does not increase the risk of disease recurrence. So are there still active tumor cells in these persistent lesions? It is generally accepted that HCG negativity suggests that there are <107 GTN tumor cells in the body and that these residual trophoblast cells are mostly killed with additional consolidation chemotherapy. However imaging lesions will still persist for some time, taking months or even years to slowly absorb, and some may undergo calcification and persist all the time. HCG testing is an important factor in the diagnosis of GTN and imaging evidence is not necessary. Therefore, from an economic point of view, HCG testing is sufficient for the follow-up of GTN patients after chemotherapy. If the HCG test is abnormal, the corresponding imaging test is chosen to detect the lesion. Of course, if there are corresponding clinical symptoms, such as irregular vaginal bleeding, chest pain, cough, hemoptysis, etc., then aggressive imaging is used. HCG conversion is considered cured by the necessary consolidation course and the disappearance of pulmonary imaging lesions is not necessary. The persistence of pulmonary imaging lesions does not increase the risk of GTN recurrence. follow-up HCG after GTN treatment is necessary, and imaging is selected based on HCG results and clinical symptoms. This article is published with permission from Dr. Jianhua Qian.