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Unformatted text preview: ',,.; ,1 l ,, l'l : i'':j,. . I "..-.-... ir . . ',,- r"af has been a swimmer : : his life, and he is helping i. :ay for college by working ':gLtard at Daytona 8each. He .. :oi ege life and hisjob, but for ' :.r is happyto be home in l_as-.-.! ior the summer. Johan's :; e. (ooked him his favorite din- . :r relebrate his first evening . - , 3t home. During the dinner ' . ersation, lohan's mother com- .r:ed on a dark spot on his ear. "Has that always been there?" she asked.lohan looked in the mirror and admitted that he had never noticed it. They agreed he should have a doctor examine it. When the doctor saw the spot, he immediately suggested that it be removed and sent to a laboratoryfor testing to determine whether it was skin cancer. Johan was fortunate; the region was only precancerous. But, he gained a new appreciation forthe association between sun exposure and skin cancer. He vowed to be more careful about using sunscreen and wearing a hat when out in the sun. After all, in North Amrica someone dies of skin cancer every hour. Cancer, the "Big C," is perhaps the disease that people in the indus- trialized world dread the most-and with good reason. Cancer touches the lives of nearly everyone. One of every three people in the United States will devlop canrer at some point in lite, and the other two are likely to have a friend or relative with cancer. ln this chapter, we consider how cancer cells escape the normal controls over cell division. We then learn about some causes of cancer and how we can reduce our risk of developing the disease. Finally, we identify some means of diagnosing and treating cancer. iorms of cancer share one characteristic uncontrolled cell :ion. Cancer cells may behave ljke aliens taking over our bodies, ihev are actually traitorous cells tiom within our own bodies. lbnormal growth of cells can form a mass ol tissoc callcd a t&nn7. .. ri(rprr.sr?i (meaning "new growth,,). However, not all tumo6 are lrrous: tumors can be eithc,r benign or malignant. A ,rrli, 'r is an abnormal mass of tissue that is surrounded by a capsule . )nnective tissue and that usually remaiDs at the site where it 'ir\. its celis do not invade surrounding tissue or sDread to distant '''r\.,illhouAh the) rJn ano do ArLrw. ln mo.r carp.. a hcniln ' , )r cloes not threaten life, because it can be removed completcly .iirger)'. Benign tumors can be harmful when they press on .:l)\' tissucs enough to interlere with the functioning of those tis_ ' ]i a "benign" tumor of that type is also inoperable, as may oc- rr.,l lurnor in thc hrain. il cdn h( l;te rhrearenirrA. lvrrr ro, t'1.t!i.Qu,utt lt not\. tumor\ lhdt can jn\Jde ,urrounding li.rue \Dread to multiplc locations throughout the body, are piopetly .!l cancerous. The spread of cancer cclls tiom one pait oi the , lo another is called metdstqsis....
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- Spring '11