What Is Cancer

Throughout our lives, healthy cells in our bodies divide and replace themselves in a controlled fashion. Cancer starts when a cell is somehow altered so that it multiplies out of control. A tumor is a mass composed of a cluster of such abnormal cells.

Most cancers form tumors, but not all tumors are cancerous.

Benign, or noncancerous, tumors do not spread to other parts of the body, and do not create new tumors. Malignant or cancerous, tumors crowd out healthy cells, interfere with body functions, and draw nutrients from body tissues.

Cancers continue to grow and spread by direct extension or through a process called metastasis, whereby the malignant cells travel through the lymphatic or blood vessels -- eventually forming new tumors in other parts of the body. 

The major types of cancer are carcinoma, sarcoma, melanoma, lymphoma, and leukemia. Carcinomas -- the most commonly diagnosed cancers -- originate in the skin, lungs, breasts, pancreas, and other organs and glands. Lymphomas are cancers of lymphocytes. Leukemia is a cancer of the blood. It does not usually form solid tumors. Sarcomas arise in bone, muscle, fat, blood vessels, cartilage, or other soft or connective tissues of the body. They are relatively uncommon. Melanomas are cancers that arise in the cells that make the pigment in the skin.

Common Signs and Symptoms of Cancer

No matter your age or health, it’s good to know the possible signs of cancer. By themselves, they aren’t enough to diagnose the disease. But they can be clues for you and your doctor so that you can find and treat the problem as soon as possible. The treatment works best early on when a tumor is small and hasn’t spread.

These symptoms don’t always mean cancer. Lots of common conditions can make you feel this way. It’s important to see your doctor so they can take a closer look at your health and take action.

Common signs and symptoms of cancer in both men and women include:

• Pain. Bone cancer often hurts from the beginning. Some brain tumors cause headaches that last for days and don’t get better with treatment. Pain can also be a late sign of cancer, so see a doctor if you don't know why it’s happening or it doesn’t go away.

• Weight loss without trying. Almost half of the people who have cancer lose weight. It’s often one of the signs that they notice first.

• Fatigue. If you’re tired all the time and rest doesn’t help, tell your doctor. Leukemia often wears you out, or you could have blood loss from colon or stomach cancer. Cancer-related weight loss can leave you exhausted, too.

• Fever. If it’s high or lasts more than 3 days, call your doctor. Some blood cancers, like lymphoma, cause a fever for days or even weeks.

• Changes in your skin. Have your doctor look at unusual or new moles, bumps, or marks on your body to be sure skin cancer isn’t lurking. Your skin can also provide clues to other kinds of cancers. If it’s darkened, looks yellow or red, itches, or sprouts more hair, or if you have an unexplained rash, it could be a sign of liver, ovarian, or kidney cancer, or lymphoma.

• Sores that don’t heal. Spots that bleed and won’t go away are also signs of skin cancer. Oral cancer can start as sores in your mouth. If you smoke, chew tobacco, or drink a lot of alcohol, you’re at higher risk.

• Cough or hoarseness that doesn’t go away. A cough is one sign of lung cancer, and hoarseness may mean cancer of your voice box (larynx) or thyroid gland.

• Unusual bleeding. Cancer can make blood show up where it shouldn’t be. Blood in your poop is a symptom of the colon or rectal cancer. And tumors along your urinary tract can cause blood in your urine.

• Anemia. This is when your body doesn’t have enough red blood cells, which are made in your bone marrow. Cancers like leukemia, lymphoma, and multiple myeloma can damage your marrow. Tumors that spread there from other places might crowd out regular red blood cells