Symptoms and Complications
Cancer can cause many different types of symptoms depending on the type of cancer and what stage it's in. Cancer cells pressing on or invading surrounding cells can cause severe pain. Organs (like the liver or pancreas) that are being invaded by the cancer can't work properly. Some symptoms, called paraneoplastic syndromes, are caused not by the tumor itself, but by chemicals or hormones produced by the tumor. The chemicals and hormones can cause an autoimmune reaction, where the body produces antibodies against itself. They can also affect the normal functioning of organs or even kill healthy cells. Symptoms like high blood pressure, low blood sugar, and diarrhea are part of paraneoplastic syndromes. They're usually not curable, unless the cancer is controlled.
Some of the complications of cancer can be life-threatening. Cancer can cause fluid to fill the sacs surrounding the heart or lung, making it very hard to breathe. Cancer can also block the veins that return blood from the upper parts of the body to the heart. This causes the veins in the chest and neck to swell. Cancer can also press on the spinal cord or spinal cord nerves, causing pain or the loss of function of the nerve. The longer a nerve has been damaged, the less likely it will recover. Hypercalcemic (high calcium) syndrome occurs when a type of cancer produces a hormone that dangerously raises the body's calcium levels or invades the bones.