Two types of lung cancer Lung cancer is divided into two types, small cell lung cancer and non-small cell lung cancer, according to its cell morphological characteristics and biological behavior. Small cell undifferentiated carcinoma The cell morphology of small cell undifferentiated carcinoma is similar to oat grain, so it is also called oat cell carcinoma. It accounts for about 20% of all lung cancers. Small cell undifferentiated carcinoma mostly originates from the larger bronchi, so most of them are central type lung cancer. Small cell undifferentiated carcinoma has low differentiation and fast growth, so lymph node metastasis and hematogenous metastasis can occur in early stage, and lymph node metastasis is extensive, and the volume of metastatic lymph nodes is often larger than the primary lung lesion. Brain metastasis and bone metastasis are most common in distant metastasis. Small cell undifferentiated carcinoma has the worst prognosis among all lung cancer types. It is highly sensitive to radiation and chemotherapy, but the majority of tumors will recur after treatment is stopped. The treatment plan for small cell undifferentiated carcinoma is obviously different from other types of lung cancer, emphasizing systemic chemotherapy as the main treatment, supplemented by local radiotherapy or surgery. Non-small cell lung cancer Other than small cell undifferentiated carcinoma, other types of lung cancer are collectively called non-small cell lung cancer, and there are mainly the following types: 1. squamous epithelial cell carcinoma. Squamous carcinoma is more closely related to smoking and generally originates from larger bronchi, which means it is mostly central lung cancer. Squamous carcinoma generally grows more slowly, has a longer course, and develops distant metastasis later, and usually first metastasizes to lymph nodes via lymphatic circulation before bloodstream metastasis occurs. Among all types of lung cancer, the highest percentage of lung cancer is treated by surgical resection. Adenocarcinoma mostly originates from the smaller bronchial mucosa epithelium, so it is mostly located in the peripheral part of the lung (i.e. peripheral type lung cancer) and is spherical in shape, close to the pleura. Adenocarcinoma is more common in women and is not significantly associated with smoking. Adenocarcinoma of the lung often has no obvious symptoms in the early stage of the disease and is often detected during chest X-ray or chest CT examination. Some cases of lung adenocarcinoma are diagnosed only after systematic examination when symptoms of distant metastasis appear. The incidence of lung adenocarcinoma has gradually increased in recent years and has occupied the first place of all lung cancer types in western countries, which may be related to the aggravation of passive smoking and atmospheric pollution. 3.Undifferentiated large cell carcinoma Undifferentiated large cell carcinoma is a relatively rare type of lung cancer, more than half of them originate from larger bronchus, with high malignancy and huge size, which can develop lymph node or bloodstream metastasis without obvious symptoms in early stage. In addition, in a few patients, two or more different histological types of components may be present in the lung tumor at the same time. For example, there is a squamous component in adenocarcinoma tissue or an adenocarcinoma component in squamous tissue and a non-small cell carcinoma component in small cell undifferentiated carcinoma. This type of lung cancer is known as mixed lung cancer.