At first, cancer, as a tiny mass of cells, causes no symptoms whatsoever. As a cancer grows, its physical presence can affect nearby tissues. Also, some cancers secrete certain substances or trigger immune reactions that cause symptoms in other parts of the body that are not near to the cancer (paraneoplastic syndromes—see see Paraneoplastic Syndromes).
Sometimes the initial indication is an abnormal result on a laboratory test done for another reason (for example anemia resulting from colon cancer found on a routine complete blood count).
Cancer affects nearby tissues by growing into or pushing on them, thus irritating or compressing them. Irritation typically causes pain. Compression may keep tissues from performing their normal functions. For example, a bladder cancer or a cancerous lymph node in the abdomen may compress the tube (ureter) connecting a kidney with the bladder, blocking the flow of urine. A lung cancer may block airflow through one segment of a lung, causing partial lung collapse and predisposing to infection. When cancer grows in an area with a lot of space, such as in the wall of the large intestine or the lung cavity, it may not cause any symptoms until it becomes quite large. In contrast, a cancer growing in a more restricted space, such as on a vocal cord, may cause symptoms (such as hoarseness) when it is relatively small. If a cancer spreads (metastasizes) to other parts of the body, the same local effects of irritation and compression eventually occur, but in the new location, so the symptoms may be quite different. Cancers that involve the membrane covering the lungs (pleura) or the baglike structure that surrounds the heart (pericardium) often ooze fluid, which collects around those organs. Large fluid collections can interfere with breathing or the pumping of the heart.
Some Complications of Cancer
Fluid accumulates in the baglike structure surrounding the heart (pericardium, or pericardial sac). This fluid puts pressure on the heart and interferes with its ability to pump blood. Fluid can accumulate when a cancer invades the pericardium and irritates it.
Fluid accumulates in the baglike structure around the lungs (pleural sac), causing shortness of breath.
Superior vena cava syndrome
Cancer partially or completely blocks the vein (superior vena cava) that drains blood from the upper part of the body into the heart. Blockage of the superior vena cava causes the veins in the upper part of the chest and neck to swell, resulting in swelling of the face, neck, and upper part of the chest.
Spinal cord compression
Cancer compresses the spinal cord or the spinal cord nerves, resulting in pain and loss of function (such as urinary or fecal incontinence). The longer the compression of the spinal cord or spinal cord nerves persists, the less likely normal nerve function will return when the compression is relieved.
The brain functions abnormally as a result of a cancer growing within it, either as a primary brain cancer or more commonly as a metastasis from a cancer elsewhere in the body. Many different symptoms can occur, including confusion, drowsiness, agitation, headaches, abnormal vision, abnormal sensations, weakness, nausea, vomiting, and seizures.
Bleeding may result from invasion and death of normal tissues and blood vessels or from the growth of abnormal, fragile blood vessels within a tumor.
Many cancers are typically painless at first, although pain may be an early symptom of some cancers, such as brain tumors that cause headache and head and neck and esophageal cancers that cause painful swallowing. As cancers grow, the first symptom is often a mild discomfort, which may steadily worsen into increasingly severe pain as the cancer enlarges. The pain may result from the cancer compressing or eroding into nerves or other structures. However, not all cancers cause severe pain. Similarly, lack of pain does not guarantee that a cancer is not growing or spreading.
At first, a cancer may bleed slightly because its blood vessels are fragile. Later, as the cancer enlarges and invades surrounding tissues, it may grow into a nearby blood vessel, causing bleeding. The bleeding may be slight and undetectable or detectable only with testing. Such is often the case in early-stage colon cancer. Or, particularly with advanced cancer, the bleeding may be more significant, even massive and life threatening.
The site of the cancer determines the site of the bleeding. Cancer anywhere along the digestive tract can cause bleeding in the stool. Cancer anywhere along the urinary tract can cause bleeding in the urine. Other cancers can bleed into internal areas of the body. Bleeding into the lungs can cause the person to cough up blood.
Certain cancers produce substances that cause excess clot formation, mainly in the veins of the legs. Blood clots in leg veins sometime break off and travel to a lung (pulmonary embolism), which can be fatal. Excessive clotting is common in people with pancreatic, lung, and other solid tumors and in people with brain tumors.
Weight loss and fatigue
Commonly, a person with cancer experiences weight loss and fatigue, which can worsen as the cancer progresses. Some people notice weight loss despite a good appetite. Others lose their appetite and may even become nauseated by food or have difficulty swallowing. They may become very thin. People with advanced cancer are often very tired. If anemia develops, these people may find that they feel tired or become short of breath with even slight activity.
Swollen lymph nodes
As a cancer begins to spread around the body, it may first spread to nearby lymph nodes, which become swollen. The swollen lymph nodes are usually painless, and they may feel hard or rubbery. They may be freely moveable, or if the cancer is more advanced, they may be stuck to the skin above, to the deeper layers of tissue below, or to each other.
Neurologic and muscular symptoms
Cancer can grow into or compress nerves or the spinal cord, causing any of several neurologic and muscular symptoms, including pain, weakness, or a change in sensation (such as tingling sensations). When a cancer grows in the brain, symptoms may be hard to pinpoint but can include confusion, dizziness, headaches, nausea, changes in vision, and seizures. Neurologic symptoms may also be part of a paraneoplastic syndrome.
Cancer can compress or block structures, such as the airways in the lungs, causing shortness of breath, cough, or pneumonia. Shortness of breath can also occur when the cancer causes a large pleural effusion, bleeding into the lungs, or anemia.