what is a cancer?How many types of cancers are there?

Question

about boilogy

Answer 1

Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue through invasion or by implantation into distant sites by metastasis. Metastasis is defined as the stage in which cancer cells are transported through the bloodstream or lymphatic system. Cancer may affect people at all ages, but risk tends to increase with age, due to the fact that DNA damage becomes more apparent in aging DNA. It is one of the principal causes of death in developed countries.

There are many types of cancer. Severity of symptoms depends on the site and character of the malignancy and whether there is metastasis. A definitive diagnosis usually requires the histologic examination of tissue by a pathologist. This tissue is obtained by biopsy or surgery. Most cancers can be treated and some cured, depending on the specific type, location, and stage. Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy. As research develops, treatments are becoming more specific for the type of cancer pathology. Drugs that target specific cancers already exist for several cancers. If untreated, cancers may eventually cause illness and death, though this is not always the case.

The unregulated growth that characterizes cancer is caused by damage to DNA, resulting in mutations to genes that encode for proteins controlling cell division. Many mutation events may be required to transform a normal cell into a malignant cell. These mutations can be caused by chemicals or physical agents called carcinogens, by close exposure to radioactive materials, or by certain viruses that can insert their DNA into the human genome. Mutations occur spontaneously, or are passed down generations as a result of germ line mutations.

Many forms of cancer are associated with exposure to environmental factors such as tobacco smoke, radiation, alcohol and certain viruses. While some of these can be avoided, there is no known way to entirely avoid the disease.

Answer 2

Cancer is a cell's genetic information gone haywire - the cell is giving instructions to make more and more and more copies, and this is what results in tumors. All cancers are genetic - all cancers are some kind of malfunction in the function of the DNA of a cell. As to how many kinds of cancer there are, nobody knows yet, but it used to be believed that prostate cancer was a single kind of cancer, and it now looks like it could be as many as 50 different kinds of cancer so as to how many types of cancer there are the answer is probably in the thousands for human beings alone.

Answer 3

cancer happens hen the genes in the body which control growth stop doing so and the growth which shud stop normally doesnt do so.

Cancers can roughly be 2 types
-carcinomas from epithelium and
-sarcomas from connective tissue,

but this is a very lame classification every part of body can develop the above two AND more depending upon the special cells there,.. for eg brain cells can form "glioma", lymph node give rise to "lymphoma", testis can have "germinomas"

Answer 4

a cancer is when a certain cell type undergoes a mutation which affects its ability to regulate it's multiplication rate. there are several proteins that can accomplish this, but bottom line, the cell begins to rapidly proliferate in an uncontrolled manner. this forms a large tumor which if it is cancerous will spread to other parts of the body and inhibit normal function of certain body systems. cancers can form in almost an part of the body with different cell types. i would estimate that there are hundreds of specific forms of cancer.