Recognizing the Warning Signs

Warning signs of cancer are often vague or very general, particularly in the early stages. Many symptoms of cancer can also be caused by other conditions. Nonetheless, even vague symptoms may provide an early warning—and an early warning means a better chance of a cure. Some of these vague symptoms include fatigue, night sweats, and new or persistent pain. A person who experiences such symptoms should be examined by a doctor. Certain symptoms are common in many cancers. These include pain, bleeding, enlarged lymph nodes, unexplained weight loss, and nausea. However, each type of cancer has its own warning signs, such as breast lumps in breast cancer, difficulty swallowing in esophageal cancer, and yellowish skin (jaundice) in pancreatic cancer.

Pain: As a cancer grows, it eventually presses on or invades surrounding tissues, often causing pain. However, many other conditions also cause pain. All cancers are initially painless and some may remain so, even after growing quite large. One should not have faith in the misconception that "all cancers produce pain" and ignore other symptoms that may occur in the absence of pain.

Bleeding: Cancer cells are not bound strongly to each other, and cancers therefore tend to be fragile and bleed easily. Cancers can also cause bleeding by growing into blood vessels, causing them to bleed. The location of bleeding depends on where the cancer is. Colon cancer usually causes blood to be detectable in the stool, and cancer of the kidney usually causes blood to be detectable in the urine. However, bleeding can have many causes other than cancer. Often bleeding is not evident, particularly if bleeding is internal. Unusual fatigue that is not improved by rest may indicate internal bleeding. Bleeding and easy bruising are typical of leukemia, but leukemia causes bleeding by a different means. The platelets in the bloodstream become fewer in number as the bone marrow (where platelets are made) produces cancer cells instead. People with low platelet levels tend to bleed easily.

Enlarged lymph nodes: Certain cancers spread initially to nearby lymph nodes. Affected lymph nodes become large and feel hard and may be difficult or impossible to move about. They are usually painless, unlike enlarged nodes from infections.

Weight loss: Some weight loss is usual in early stages of cancer; severe weight loss (cachexia) often occurs as the cancer advances. In response to the cancer, the body may release chemicals called cytokines (two such cytokines are tumor necrosis factor and interleukin 6). The release of cytokines can cause weight loss. Weight loss may also result from side effects of cancer treatment, such as nausea or vomiting. A person may be unable to eat or to digest food because of abnormalities resulting from the cancer, such as blockage of the throat, esophagus, or intestine. Weight loss may also occur because the person is depressed or just too tired to eat.

Nausea: Nausea may result from changes in the levels of substances in the blood (such as increased levels of calcium, decreased levels of sodium, or high levels of urea in the blood). The spread of cancer (metastasis) to the liver or brain can also cause nausea. Many people who take chemotherapy drugs or powerful pain relievers, such as the opioids used to treat cancer pain, experience nausea as a side effect.

Other symptoms: Cancers may be found because of symptoms created by the original (primary) tumor. They may also be found because they have spread to another part of the body and caused symptoms there. For example, bone pain may result from a cancer that has spread to bone. However some bone pain, such as pain in joints, is common in old age and usually does not signify cancer. Weakness or altered sensation in one part of the body can result from cancer that has spread to the brain. But identical symptoms can be caused by a stroke.

A cancer may release substances that act as hormones. For example, some cancers release a substance that mimics the effects of parathyroid hormone. This substance causes the level of calcium in the blood to increase and thereby leads to such symptoms as abdominal pain, muscle weakness, diarrhea, and even mental confusion. Another substance released by a cancer can cause effects similar to those of cortisol, producing a very full, chubby facial appearance and stretch marks in the skin.