Small cell lung cancer accounts for 15% of all lung cancers and approximately 98% of small cell lung cancers are associated with smoking. Others are associated with environmental and genetic factors. Clinical manifestations Cough, dyspnea, weight loss and debility with or without obstructive pneumonia, which are often caused by larger masses at the hilum and enlarged mediastinal lymph nodes. The neurological and endocrine paraneoplastic syndromes caused by tumors include Lan-I syndrome, cancer-related encephalomyelitis and sensory neuropathy, as well as Cushing’s syndrome and hyponatremia. Li Shengya, Department of Internal Medicine, Henan Cancer Hospital Prognostic factors Poor body mass, extensive stage, weight loss, multiple sites of tumor invasion and oversized tumor are important poor prognostic factors. In the limited stage, women, under 70 years old, stage I and normal LDH have better prognosis; in the extensive stage, those with normal LDH and single metastases have good prognosis, the number of involved organs is negatively correlated with prognosis, and the prognosis of liver metastases is worse. Those with endocrine paraneoplastic syndrome have a poor prognosis. Examination methods Physical examination, chest X-ray, chest and abdomen CT, head MRI, bone scan. PET scan if necessary. About 30% of patients with normal or asymptomatic alkaline phosphatase levels have positive bone scans; about 10% to 15% of newly diagnosed patients have central nervous system metastases detected by cranial CT or MRI scans, and 30% of them are asymptomatic. Due to the rapid growth of small cell tumors, most patients develop typical symptoms within 8 weeks, and the progression of the disease is significantly accelerated afterwards; do not delay treatment by spending too much time on examination and staging.