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 term "cancer" encompasses more than 100 diseases affecting nearly every part of the body, and all are potentially life-threatening.
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 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 skin.
Cancer has been recognized for thousands of years as a human ailment, yet only in the past century has medical science understood what cancer really is and how it progresses. Cancer specialists, called oncologists, have made remarkable advances in cancer diagnosis, prevention, and treatment. Today, more people diagnosed with cancer are living longer. However, some forms of the disease remain frustratingly difficult to treat. Modern treatment can significantly improve quality of life and may extend survival.
Katika maisha yetu yote, chembe zetu zenye afya hugawanyika na kubadilika kwa njia inayodhibitiwa. Saratani huanza wakati chembe inapobadilika kwa njia fulani hivi kwamba huongezeka bila kudhibitiwa. Uvimbe ni chembe nyingi zilizofanyizwa na chembe zisizo za kawaida. Aina nyingi za kansa hufanyiza uvimbe, lakini si uvimbe wote wenye kansa. Ugonjwa wa kansa, au ugonjwa usio na kansa, hauwezi kuenea kwenye sehemu nyingine za mwili, na hauwezi kuunda uvimbe mpya. Matumbo mabaya, au kansa, huondoa chembe zenye afya, huingilia kazi za mwili, na kuchukua virutubisho kutoka kwa tishu za mwili. Saratani huendelea kukua na kuenea kwa kupanuka moja kwa moja au kupitia mchakato unaoitwa metastasis, ambapo seli mbaya husafiri kupitia mishipa ya lymphatic au damu - hatimaye kuunda uvimbe mpya katika sehemu nyingine za mwili. "Jina ""Kansa"" linatia ndani magonjwa zaidi ya 100 yanayoathiri karibu kila sehemu ya mwili, na yote yanaweza kuhatarisha uhai." Aina kuu za kansa ni kansa, sarcoma, melanoma, lymphoma, na leukemia. Karsinoma - aina ya kansa inayogunduliwa kwa kawaida - hutokea kwenye ngozi, mapafu, matiti, kongosho, na viungo na tezi nyinginezo. Lymphomas ni kansa ya lymphocytes. Leukemia ni kansa ya damu. Kwa kawaida haifanyi uvimbe imara. Sarcomas hutokea katika mifupa, misuli, mafuta, mishipa ya damu, cartilage, au tishu nyingine laini au za kuunganisha za mwili. Wao si wa kawaida sana. Melanoma ni aina ya kansa inayotokea katika chembe zinazotengeneza rangi ya ngozi. Ugonjwa wa kansa umekuwa ukitambuliwa kwa maelfu ya miaka kama ugonjwa wa binadamu, lakini ni katika karne iliyopita tu ambapo sayansi ya kitiba imeelewa ni nini hasa kansa na jinsi inavyoendelea. Wataalamu wa kansa, wanaoitwa wataalamu wa kansa, wamefanya maendeleo makubwa katika utambuzi, kuzuia, na kutibu kansa. Leo, watu wengi zaidi wanaogunduliwa kuwa na kansa wanaishi muda mrefu zaidi. Hata hivyo, aina fulani za ugonjwa huo bado ni vigumu kutibu. Matibabu ya kisasa yanaweza kuboresha sana hali ya maisha na yaweza kupanua muda wa kuishi.