It is quite common for malignant tumors originating from other parts of the body to metastasize to the lungs through the blood or lymphatic channels. According to statistics, about 20% to 30% of cases of death from malignant tumors have lung metastasis. The time of lung metastasis of malignant tumors varies. In most cases, metastasis occurs within 3 years after the appearance of the primary tumor, and in some cases, it lasts for more than 10 years. However, in a few cases, lung metastases are discovered earlier than the primary tumor. Primary malignant tumors that metastasize to the lungs mostly come from the breast, bones, digestive tract, and genitourinary system. Most lung metastatic tumors are multiple lesions throughout both lungs, of varying sizes and uniform density. There is currently no effective treatment for these advanced cancer cases. In a few cases, if there is only a single isolated metastatic lesion in the lung, external surgical treatment can be considered.