The most common symptoms of lung cancer include coughing, particularly irritating coughs, and symptoms of coughing up blood. The blood in the sputum may appear as spots, streaks, or intermittent small amounts. Other symptoms include difficulty breathing and chest pain, as well as potential tightness in the chest, shortness of breath, and fever. Secondly, if lung cancer grows within the thoracic cavity and spreads, invading nearby tissues and organs, it can produce secondary symptoms. For example, paralysis of the phrenic nerve on the same side may lead to difficulty breathing and belching. Compression of the recurrent laryngeal nerve may cause hoarseness; compression of the superior vena cava can lead to distended veins in the face, neck, and upper limbs; subcutaneous edema; and if the pleura is invaded, it can cause pleural effusion, among other symptoms. If lung cancer metastasizes through the bloodstream, it may spread to the brain and potentially lead to symptoms such as headaches, nausea, and vomiting. Metastasis to different regions of the brain might cause various symptoms, including seizures, mental confusion, and vision impairment. In a minority of cases, lung cancer may produce endocrine substances, possibly leading to symptoms like severe muscle weakness, bone and joint pain, and other such symptoms.