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).

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. Cancer anywhere may compress a blood vessel, shutting off blood flow or causing bleeding. When cancer grows in an area with a lot of space, such as in the wall of the large intestine, 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.

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Some Complications of Cancer Complication Description Cardiac tamponade 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. Pleural effusion 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. Brain dysfunction 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 Cancer grows into and erodes nearby blood vessels. Serious, even fatal, bleeding can result from cancers in areas containing many large blood vessels, such as the neck and chest.

What Are Paraneoplastic Syndromes?
Paraneoplastic syndromes occur when a cancer produces one or more substances that circulate in the bloodstream to cause symptoms at sites distant from the tumor. These substances can affect the function of other tissues and organs, resulting in a variety of symptoms. Paraneoplastic syndromes may affect many different organ systems, including the nervous system and the endocrine (hormone) system, causing such problems as low blood sugar, diarrhea, or high blood pressure. General syndromes such as the development of fever, night sweats, and loss of weight and appetite can be experienced by many people with cancer. Most of the syndromes discussed below are uncommon, and most cancer patients do not experience these more specific paraneoplastic syndromes. Neurologic syndromes: Polyneuropathy is a dysfunction of peripheral nerves, resulting in weakness, loss of sensation, and reduced reflexes. Subacute sensory neuropathy is a rare form of polyneuropathy that sometimes develops before the cancer is diagnosed. It causes a disabling loss of sensation and incoordination but little weakness. Paraneoplastic cerebellar degeneration occurs rarely in patients with breast cancer, ovarian cancer, small cell carcinoma of the lung, or other solid tumors. This disorder may be caused by an autoantibody (an antibody that attacks the body's own tissues) that destroys the cerebellum. Symptoms can include unsteadiness in walking, incoordination of the arms and legs, difficulty speaking, dizziness, and double vision. Symptoms may appear before the cancer is detected. Uncontrollable eye movements (opsoclonus) and quick contractions of the arms and legs (myoclonus) can occur in some children with neuroblastoma. Subacute motor neuronopathy occurs in some people with Hodgkin and non-Hodgkin lymphoma. The nerve cells of the spinal cord are affected, weakening the arms and legs. Eaton-Lambert syndrome occurs in some people with small cell carcinoma of the lung. This syndrome is characterized by extreme muscle weakness caused by lack of proper activation of the muscle by the nerve. Thymoma is a rare tumor that can be associated with myasthenia gravis, a syndrome of weakness resulting from antibodies that damage the nerve connections in muscle tissue. Endocrine syndromes: Small cell carcinoma of the lung may secrete a substance that stimulates the adrenal gland to produce increased hormone levels, which can cause weakness, weight gain, and high blood pressure (Cushing's syndrome). Small cell carcinoma of the lung may also produce antidiuretic hormone, causing water retention, decreased sodium levels, weakness, confusion, and seizures in some people. Very high calcium levels in the blood (hypercalcemic syndrome) may occur in people with solid tumors or leukemias. This can occur when the cancer secretes a hormone-like substance in the blood that causes release of calcium from bone. High calcium levels may also result if the cancer directly invades bone, thereby releasing calcium into the bloodstream. As a result of the high calcium levels in the blood, the person develops confusion, which can progress to coma and even death. Excessive production of other hormones can cause carcinoid syndrome---flushing, wheezing, diarrhea, and heart valve problems. Other syndromes: Polymyositis is muscle weakness and soreness resulting from muscle inflammation. When polymyositis is accompanied by skin inflammation, the condition is called dermatomyositis. Hypertrophic osteoarthropathy can occur in people with lung cancer. This syndrome alters the shape of the fingers and toes and can cause painful swelling of some joints.

Pain

Cancers are typically painless at first. As they 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.

Bleeding

At first, a cancer may bleed slightly because its cells are not well attached to each other and 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 gastrointestinal 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.

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; the loss of underlying fat is particularly noticeable in the face. People with advanced cancer are often very tired and sleep many hours a day. 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 may be painless or tender, 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.

Depression

Cancer often results in depression. Depression can be related to the symptoms of the illness, a fear of dying, or a loss of independence. Additionally, some cancers may produce substances that directly cause depression by affecting the brain.

Neurologic and Muscular Symptoms

Cancer can grow into or compress nerves, causing any of several neurologic and muscular symptoms, including a change in sensation (such as tingling sensations) or muscle weakness. 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.

Respiratory Symptoms

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.

Last full review/revision October 2006 by Matthew G. Fury, MD