Tumors, also called neoplasms, are abnormal masses of tissue created by uncontrolled cell division which serve no physiological purpose. A tumor may be either benign or malignant. Benign tumors are self-contained, non-lethal, and grow more slowly than malignant ones. Malignant tumors are cancerous growths which expand quickly and can metastasize, or spread to other areas of the body.
Malignant tumors grow by invading nearby cells and spread to other parts of the body through a process called metastasis. Cells break off the tumor, enter the bloodstream or lymphatic system, and spread to another area, infecting additional tissue. This is how a tumor which starts in one part of the body, such as the breast or prostate, can spread to another type of tissue, such as the bones.
If a suspicious tumor is present, it is common for a doctor to do a biopsy, or to cut off a small sample of the tumor, which is then examined under a microscope. The cells in malignant tumors are different the normal cells in a number of ways. Normal cells are uniform in shape with a nucleus containing chromatin and a nucleolus which contains RNA and DNA. Cancerous tumors have irregular cells with large irregular nucleoli and chromatin. In addition, malignant cells do not stick together like normal cells, and they stain differently under a microscope.
The TNM classification system designed by the International Union against Cancer attempts to classify malignant tumors according to the extent to which they have spread through the body. The T represents the size of the tumor, the N represents any lymph nodes which may be engaged, and the M stand for the extent of metastasis, or how far the cancer has spread throughout the body. This method is used for lung, colon and stomach cancers, among others.
Brain and spinal tumors use a classification method ratified by the World Health Organization which is based upon the premise that different types of malignant nervous system tumors are a result of the abnormal growth of specific types of cells. In this system, the tumor is classified by the type of cell it resembles. Once the tumor is classified, it is given a numerical grading signifying the degree of malignancy. The more aggressive the tumor, the higher the number assigned.
Symptoms vary depending upon the type and location of the mass, and some cancerous tumors have no symptoms until the disease has reached the most aggressive stage. Symptoms of colon cancer include diarrhea, constipation, bleeding and anemia while lung cancer is accompanied by coughing, shortness of breath and chest pains. Fatigue, pain, fever, loss of appetite and weight loss are also symptoms of various malignant tumors. In addition to a biopsy, other diagnostic tools include blood tests, magnetic resonance imaging (MRI) scans, X-ray, computer tomography (CT), and positron emission tomography (PET).
The treatment of cancerous tumors depends upon the type of cancer, the location of the tumor, and the degree of metastasis, among other factors. Whenever possible, surgical removal is recommended to prevent further spread of the disease. If the tumor has not spread, additional treatment may not be necessary. If the spread is confined to a few lymph nodes, these are also removed. Certain types of cancer or those which have spread to other areas of the body often require radiation, chemotherapy, or a combination of both.