How to classify lung cancer

I. Tumor typing by naked-eye morphology (1) Intratubular type: The tumor is limited to the lumen of larger bronchial tubes, showing polypoid or cauliflower-like protrusion into the lumen, and a few of them have tips. The tumor may also spread along the wall of the tube in the form of a tubular sleeve, and most of them do not have extra-tubular infiltration. (2) Tubular wall infiltration: the tumor invades the wall of the larger bronchial tubes, the mucosal folds of the tubular wall disappear, and the surface is granular or granulomatous. The wall is thickened and the lumen is narrowed, and often infiltrates into the lung tissue outside the wall. The bronchial wall structures are still present as seen in the section of the mass. (3) Nodular type: the mass is round or round-like, with a diameter of less than 5cm, and when it is clearly demarcated from the surrounding tissues, the edge of the mass is often lobulated. (4)Massive type The mass is irregular in shape, with a diameter greater than 5cm, and the edge is large lobulated, with unclear demarcation from the surrounding lung tissues. (5) Diffusely infiltrating type: the tumor does not form a limited mass, but is diffusely infiltrating, involving most of the lobes or segments of the lung, similar to lobar pneumonia. Because the biological behavior of small cell lung cancer is significantly different from other epithelial cancers (squamous carcinoma, adenocarcinoma, adenosquamous carcinoma, large cell carcinoma), i.e., clinically, it is highly malignant, with extensive distant metastases occurring in the early stage, and it is more sensitive to chemotherapy and radiotherapy, and therefore, the principle of treatment is also different from that of other epithelial cancers. Therefore, from the clinical point of view, at present, the world tends to roughly classify these two types of lung cancers with different biological behaviors into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), which includes other epithelial carcinomas except small cell carcinoma. Classification according to anatomical sites (1) Central lung cancer: Cancer occurring above the segmental bronchus and up to the main bronchus is called central lung cancer, which accounts for about 3/4 of the cases, and squamous epithelial cell carcinoma and small cell undifferentiated carcinoma are more common. （Tumors occurring below the segmental bronchus are called peripheral type, accounting for about 1/4 of the cases, and adenocarcinoma is more common. At present, the histological classification of cancer at home and abroad is still not very uniform, but most of them are divided into squamous epithelial carcinoma, small cell undifferentiated carcinoma, large cell undifferentiated carcinoma and adenocarcinoma according to the degree of cell differentiation and morphological characteristics. （Squamous epithelial cell carcinoma (referred to as squamous carcinoma) is the most common type, accounting for about 40%-50% of primary lung cancers. It is mostly found in elderly men and is closely related to smoking. Lung cancer of central type is common and has a tendency to grow into the lumen, often causing bronchial stenosis at an early stage, leading to atelectasis, or obstructive pneumonia. Cancer tissues are easily degenerated and necrotic, forming cavities or cancerous lung abscesses. Squamous carcinoma grows slowly and metastasizes late, with relatively more chances of surgical resection and a higher 5-year survival rate, but radiation therapy and chemotherapy are not as sensitive as that of small cell undifferentiated carcinoma. Due to chronic irritation and injury, loss of cilia, squamous metaplasia of basal cells, atypical hyperplasia and dysplasia of columnar epithelial cells of bronchial mucosa, they are most likely to mutate into carcinoma. Typical squamous epithelioid arrangement. Electron microscopy: there are a large number of nuclei connected with tension fiber bundles between cancer cells. Sometimes, squamous carcinoma and adenocarcinoma are mixed, which is called mixed lung cancer (squamous adenocarcinoma). (ii) Small cell undifferentiated carcinoma (referred to as small cell carcinoma) is the most malignant type of lung cancer, accounting for about 1/5 of the primary lung cancers, and the patients are young, mostly around 40-50 years old, with a history of smoking. It mostly occurs in the large bronchial tubes near the hilum, tends to grow in the submucosal layer, often invades the extra-tubular lung parenchyma, and is easy to merge with hilar and mediastinal lymph nodes to form clusters. The cancer cells grow fast, have strong invasive power and early distant metastasis. 60%-100% of blood vessels are found to be invaded during surgery, and autopsy proves that 80%-100% of them have lymph node metastasis, which often metastasize to organs such as brain, liver, bone and adrenal gland. This type is sensitive to radiotherapy and chemotherapy. The cancer cells are mostly rounded or prismatic with little cytoplasm, resembling lymphocytes, oat cell type and intermediate type possibly originating from Kulchitiky cells or silversmith cells of the neural ectoderm. Nucleocyte plasma contains neurosecretory granules with endocrine and chemoreceptor functions, which can secrete peptides such as 5-hydroxytryptamine, catecholamine, histamine, and kinin, and can cause paraneoplastic syndrome. (III) Large-cell undifferentiated carcinoma (large-cell carcinoma) can occur in the bronchial tubes near the hilum or at the edge of the lungs. The cells are large but with different sizes, often polygonal or irregular, arranged in solid nests, with large hemorrhagic necrosis; the nuclei of the cancer cells are large, the nucleolus is obvious, the nuclear schizophrenia is common, the cytoplasm is abundant, and it can be divided into the giant-cell type and the clear-cell type. The nuclei of cancer cells are large, nucleoli are obvious, nuclear schizophrenia is common and cytoplasm is abundant. Clear cell type is easily mistaken for metastatic renal adenocarcinoma. The metastasis of large cell carcinoma is later than that of small cell undifferentiated carcinoma, and the chance of surgical resection is higher. （Adenocarcinoma is more common in females (female food), which has little relationship with smoking, and mostly grows in the mucous glands of small bronchial tubes at the edge of lungs, therefore, adenocarcinoma is the most common among peripheral lung cancers. Adenocarcinoma accounts for about 25% of primary lung cancer. Adenocarcinoma tends to grow outside the ducts, but it can also spread through the alveolar wall, often forming a mass with a diameter of 2-4 cm at the lung margin. Adenocarcinoma is rich in blood vessels, so local infiltration and hematogenous metastasis are earlier than squamous carcinoma. It is easy to metastasize to liver, brain and bone, and more likely to involve pleura and cause pleural effusion.