1. Is lung cancer prone to brain metastasis? Brain metastases account for about 10% of intracranial tumors, of which 30% to 60% originate from primary lung cancer. Thus, lung cancer is the most common primary focus of brain metastases. 2. What are the types of lung cancer? Lung cancer is divided into small cell lung cancer and non-small cell lung cancer. Small cell lung cancer accounts for about 20% of lung cancer and can be divided into three subtypes: oat cell type, intermediate cell type and mixed type. Non-small cell lung cancer is a large group of lung cancers including adenocarcinoma, squamous carcinoma, large cell lung cancer, fine bronchoalveolar carcinoma and other rare lung cancers, accounting for about 80% of lung cancers. 3. What are the characteristics of brain metastasis from small cell lung cancer? Small cell lung cancer accounts for about 20% of lung cancer and can be divided into three subtypes: oat cell type, intermediate cell type and mixed type. Brain metastasis occurs more often and earlier in small cell lung cancer than in non-small cell lung cancer, and most patients have metastasis by the time they are diagnosed, and some even come to the clinic with symptoms caused by metastases and are only found to have small cell lung cancer on further examination. In the case of brain metastases, they usually occur within the first two years after diagnosis. More than 30% of small cell lung cancers have brain metastases at the time of diagnosis, and 50% of brain metastases can be found at autopsy. The risk of brain metastases within 2 years in patients with small cell lung cancer who do not receive preventive treatment of the central nervous system is as high as 50% to 80%. The proportion of patients with asymptomatic brain metastases detected by MRI at the time of presentation is as high as 15%. Multiple brain metastases and extracranial metastases often suggest a poor prognosis. 4. Which parts of the body are prone to metastasis in non-small cell lung cancer? What are the characteristics of brain metastasis of non-small cell lung cancer? Non-small cell lung cancer is a large group of lung cancers including adenocarcinoma, squamous carcinoma, large cell lung cancer, bronchoalveolar carcinoma and other rare lung cancers, accounting for about 80% of lung cancers. Bone, adrenal gland and brain are the most common sites of metastasis in non-small cell lung cancer, among which metastasis to brain accounts for about 1/3, multifocal metastasis is common, and only 30% are single metastasis. Two-thirds are located supratentorially and one-third are located infratentorially.