Most people are diagnosed with lung cancer in one of two ways, either by going to the hospital to see a doctor after a specific clinical presentation, or out of a routine physical exam or by chance during a visit for another condition, such as an x-ray chest x-ray during a heart appointment. If it is the latter way, then you are lucky because the lung cancer may still be at an early stage at that point, and if it is the former way it may be worse. In this chapter, we will try to talk about the common symptoms of lung cancer in simple language and tell you what tests are available to help us finalize the diagnosis of lung cancer. Common symptoms of lung cancer The vast majority of people go to the doctor because they have new symptoms or a new change in a long history of discomfort. Unfortunately, most lung cancer patients only develop symptoms when they reach a more advanced stage. The symptoms of lung cancer are mainly divided into three categories, one is caused by tumor irritation, invasion and obstruction of airways and lung tissues inside the lung; one is caused by lung cancer invasion outside the lung but still confined to the pleural cavity, such as pleural effusion, chest pain, or obstructive manifestations after large vessel heart involvement; and special manifestations caused if lung cancer metastasizes to other locations in the body. Of course, lung cancer will also secrete hormone-like substances, which will cause specific systemic or local manifestations. The most common clinical manifestations of lung cancer are cough, blood in the sputum, chest pain, shortness of breath, weakness, and weight loss. It is worth noting that there are other diseases that can also cause one or several of the above symptoms, such as emphysema, heart failure, heartburn after gastroesophageal reflux. This is when we need to go to the hospital for a targeted examination. It is especially important to pay attention when the following occur: cough that lasts for several weeks or a significant worsening of previous cough symptoms; blood in the sputum, often with bright red blood; sudden onset of hoarseness abnormal shortness of breath manifestation, especially if it lasts for several weeks without change or gets progressively worse; new onset of persistent chest pain that does not improve or gets progressively worse after several weeks or sudden worsening of previous chronic chest pain; new onset of weakness In addition to the above symptoms, there are also some other symptoms that indicate that the tumor may be in the progressive stage, such as large mouthful of blood or shortness of breath and inability to lie down. This is often because the tumor has started to seriously erode the lung, or there is a large amount of cancerous pleural effusion, or the airway is severely blocked, thus affecting your breathing function. When there is unexplained pain in other parts of the body, it may be due to cancer cells metastasizing to the bones. If neurological symptoms such as headache and fainting occur, it indicates that brain metastasis may have appeared. Paraneoplastic syndrome Sometimes patients with lung cancer may develop a series of systemic symptoms or signs that seem unrelated to the lungs, or the respiratory system, but these manifestations are indeed related to lung cancer, which we call paraneoplastic syndrome. These symptoms can sometimes appear very early. Paraneoplastic syndrome is mainly due to the reaction of specific substances secreted by tumor cells similar to endocrine hormones in human body after specific action on body organs, or the self-protection mechanism of human body for tumor is at work, inducing paraneoplastic neurological reaction. When lung cancer patients have tumor-related endocrine abnormalities, they often show abnormal secretion of hormones by tumor cells, which may be exactly the same as the normal secretion of hormones by certain glands in the body, but show uncontrolled overproduction, which may lead to abnormal calcium and sodium ion levels in the body or abnormally high corticosteroid levels. Stroke. It can also lead to very dangerous cardiac arrhythmias. Paraneoplastic syndrome can be characterized by weakness and sensory abnormalities. It may also affect abnormalities in the bones, blood system, kidneys, and overall sensation. When the tumor is well controlled or cured, all these symptoms will disappear naturally.