A middle-aged female, who visited the dermatology department for recurrent rash, had no significant effect after several months of treatment. Later, a mass in the lung was found on CT, which was diagnosed as lung cancer by puncture and required surgery. After surgery to remove the lung tumor, the rash also magically disappeared. Although the lung cancer was finally diagnosed as early stage, it was delayed for several months. In clinical practice, we can find that some lung cancer patients do not have typical symptoms such as coughing and coughing up blood, but mainly manifest with rash, osteoarthrosis and other extra-pulmonary symptoms, which is called “paraneoplastic syndrome”. 1.What is “paraneoplastic syndrome”? Some of the symptoms appearing in tumor patients are not caused by the direct invasion of the original tissues and organs by the tumor, but by the dysfunction of other distant organs, which is commonly known as “tumor of one organ causes dysfunction of another organ”. 2.What is the significance of understanding “paraneoplastic syndrome”? Some of the symptoms of “paraneoplastic syndrome” can exist for years before the tumor is detected, so understanding these symptoms is very meaningful in clinical treatment, not only for early detection of lung cancer, but also for observing the treatment effect. 3.What are the “paraneoplastic syndromes” related to lung cancer? (1) Acanthosis nigricans is mainly manifested as “blackened skin”, i.e. gray-brown patches appearing in the folds of joints such as the neck and armpits, which are symmetrically distributed. It is commonly seen in lung adenocarcinoma and also in gastric cancer. (2) Tripe palm The main manifestation is the thickening of palm and increase of folds, accompanied by pigmentation, similar to “tripe”. It is commonly seen in lung cancer. (3) Pestle finger Mainly manifested as thickening and enlargement of the end of the finger, with severe pain and redness around the nail. Commonly seen in lung cancer. (4) Hypertrophic osteoarthropathy mainly manifests as thickening and enlargement of joints with redness and swelling, pain at night, which can involve both large and small joints, and later causes stiffness and immobility of joints. It is commonly seen in lung cancer. (5) Eaton-Lambert syndrome The main symptoms are weakness of the proximal extremities and weakness of the pelvic muscles. It needs to be differentiated from myasthenia gravis. It is commonly seen in small cell lung cancer. (6) Dermatomyositis The main manifestations are weakness of the limbs, characteristic rash, and respiratory distress in severe cases. It can be seen in lung cancer, esophageal cancer, thymoma and other tumors. (7) Neurological symptoms: Ataxia, strabismus, hemiparesis, hand and foot numbness and other neurodegenerative symptoms. It may appear several years earlier than the tumor. It is common in small cell lung cancer. (8) Ectopic ACTH syndrome mainly manifests as full moon face, buffalo back, skin pigmentation and other symptoms of Cushing’s syndrome, which may also be accompanied by muscle weakness. It is commonly seen in small cell lung cancer, thymic carcinoid tumor, bronchial carcinoid tumor, and also pancreatic cancer. (9) Antidiuretic hormone dysregulation syndrome mainly manifests as malignant, vomiting, mental abnormalities and other hyponatremic manifestations, and in severe cases, spinal cord injury and craniocerebral injury may occur. It is commonly seen in lung oat cell carcinoma, also seen in urological tumor, leukemia, head and neck tumor. (10) Lung cancer with carcinoma syndrome Secretion of adrenocorticotropic hormone – full moon face, buffalo shoulder. Secretion of thyroid-like hormone – polyuria, thirst, constipation, tachycardia, arrhythmia, high blood calcium, low blood phosphorus. Secretion of gonadotropins – gynecomastia, often with hypertrophic osteoarthropathy. Secretion of antidiuretic hormone – dilute hyponatremia, sodium syndrome, general edema, drowsiness, disorientation, water intoxication. 4.What should I do if the above symptoms appear? After all, the incidence of “paraneoplastic syndrome” of lung cancer is small, so the occurrence of the above symptoms does not necessarily mean that you have lung cancer. Generally speaking, if the above symptoms appear, you should first go to the corresponding internal medicine department for consultation. If the treatment effect is not obvious, patients with high risk factors of lung cancer or middle-aged or above should undergo chest CT examination. If CT or other related examinations suggest a mass in the lung, further evaluation of the need for surgical treatment is required. Most symptoms will disappear with the removal of the mass.