Overview of Cancer

What is cancer?
It is the nature of cells to divide and increase their number in a process called mitosis. Normal cells divide to replace those lost, or to repair injuries only, then stop dividing.

Cancer is an abnormal, continuous multiplying of cells. The cells divide uncontrollably and may grow into adjacent tissue or spread to distant parts of the body. The mass of cancer cells eventually become large enough to produce lumps, masses, or tumors that can be detected, which can be benign or malignant:

• benign tumors:

• are not cancerous
• can usually be removed
• do not come back in most cases
• do not spread to other parts of the body, and the cells do not invade other tissues

• malignant tumors:

• are cancerous
• can invade and damage nearby tissues and organs
• metastasize (cancer cells break away from a malignant tumor and enter the bloodstream or lymphatic system to form secondary tumors in other parts of the body)

The smallest cancer that can be detected by examination, x-ray, or scan is slightly less than one-fourth of an inch in diameter and contains between a million to a billion cancer cells.

What are the general categories of cancers?
There are several general categories of cancer, with carcinomas and adenocarcinomas being the most common:

• Carcinomas are cancers that occur in epithelial surfaces -- the cells that form the outer surface of the body to line or cover the body's cavities, tubes and passageways.

• Adenocarcinomas are cancers that form on a glandular surface, such as the lung, breast, prostate, ovary, or kidney.

• Sarcomas are cancers that occur in supporting structures, such as bone, muscle, cartilage, fat, or fibrous tissue.

• Leukemias and lymphomas are cancers that occur in blood cell elements.

Brain cancers, nerve cancers, melanomas, and certain testicular and ovarian cancers do not fall into a general category.

What are primary cancers?
Cancers begin in a single cell, and that cell is the site of the primary cancer. The cancer is named for the primary site of origin, such as skin, colon, or breast. For example:

• When cancer is found in the liver that originated in the colon it is called colon cancer that has metastasized to the liver, not liver cancer.

• Liver cancers are those that originated from a liver cell. If it spreads to the lung, it is still liver cancer, not lung cancer.

• When cancer spreads to the regional lymph nodes, those nodes are said to contain metastatic cancer. (Cancers that originate in the lymph cells of a node are called lymphomas.)

What are metastatic cancers?
Cancer can spread from its original location to other parts of the body.

• Spreading may occur by direct extension or invasion into adjacent tissues.

• Systemic spread throughout the body may occur by way of the:

• blood system -- arteries and veins take blood to and from all areas of the body

• lymphatic system -- a network of lymphatic vessels in all areas of the body that drain and filter infectious agents

• cerebrospinal fluid

When cancer spreads to another part of the body, it is called metastatic cancer.

• tobacco use -- including smoking cigarettes and cigars, and using "smokeless tobacco" or snuff
• a high-fat diet has been linked to certain types of cancer
• obesity has been linked to certain types of cancer
• ultraviolet radiation from the sun and other sources
• alcohol consumption in large quantities
• excessive radiation exposure from x-rays
• environmental exposure to chemicals
• hormone replacement therapy of estrogen has been linked to breast and uterine cancers
• diethylstilbestrol (DES) exposure prior to birth
• family history of certain types of cancer

What are the symptoms of cancer?
Although there may be other symptoms for specific types of cancers, generally, signs and symptoms include:

• change in bowel or bladder habits

• a sore that does not heal

• unusual bleeding or discharge

• thickening or lump in any part of the body

• indigestion

• difficulty swallowing

• obvious change in a wart or mole

• nagging cough or hoarseness

These may be caused by cancer or less serious conditions. Consult your physician for a diagnosis.

Can cancer be prevented?
Although cancer may not be preventable, paying close attention to the risk factors listed above, having routine physical examinations by your physician, and participating in routine screening programs can provide the best chance for early detection and successful treatment. Routine screenings include:

Men and Women

• Regular skin self-examination and physician examination
• Annual fecal occult blood test after age 50
• Annual digital rectal examination
• Sigmoidoscopy every 3 to 5 years after age 50
• Monthly oral self-examination and regular physician examination

Men

• Annual prostate examination by physician after age 40
• Monthly testicular self-examination and annual physician examination

Women

• Monthly breast self-examination after age 20

• Annual breast examination by physician

• Annual mammograms after age 40

• Regular pelvic examinations by physician

• Annual Pap test after age 18 or after you become sexually active