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Lung cancer. Brain tumors. Breast cancer. Every organ in your body is vulnerable to creating abnormal cells that attack you healthy tissue, but there's one body part where just doesn't seem to be “a thing”.
Heart disease is the leading cause of death in the United States, according to the CDC, so why do you rarely hear about cardiac cancer? Heart cancer does exist-it's just incredibly rare. Primary heart cancer affects about 50 people in one million, says Salim Hayek, MD, a cardiologist at the University of Michigan's Frankel Cardiovascular Center who specializes in cardio-oncology. To put that in perspective, about one in eight American women will be affected by invasive breast cancer.
As cells are growing and dividing, a mutation can occur, whether from genetic or environmental factors, says Steve Xydas, MD, chief of the Columbia University Division of Cardiac and Thoracic Surgery at Mount Sinai Medical Center and co-director of the Mount Sinai Heart Institute. Those mutated cells start rapidly growing and dividing, ignoring signals designed to tell them to die. Eventually, they can form a cancerous tumor.
Ironically, the factors that make the heart so vulnerable to disease are also thought to make it less vulnerable to cancer, says Dr, Hayek, “Most cardiac muscle cells, also known as myocytes，cannot divide and grow in number," he says. "These are cells that are so organized and specialized in their function that they have many mechanisms and checkpoints that will not allow them to return to an earlier stage of immaturity and regenerate."Without being able to regenerate quickly, it's hard for the heart to repair damage from cardiac events-but that also doesn't leave the door open very wide for mutations to grow into cancer. Meanwhile, the heart also might be better protected from environmental risk factors, says Dr, Xydas.“There is less ability to expose the heart to carcinogens(致癌物),as opposed to inhaling smoke to the lungs, for instance,”he says.
There are few risk factors for heart cancer, but some conditions, such as Carney complex, raise the risk of tumors. Even then, the vast majority of tumors-including the ones associated with Carney complex-are benign (良性的), not cancerous. Unlike other benign lumps, which are generally harmless, these ones should be removed to keep them from blocking blood flow, says Dr. Xydas Cancer can spread to the heart from other areas, but nearly 10 percent of fatal cancer cases have spread to the heart,”say Dr Hayek.“These cancers ,when metastasized reach the heart commonly through the bloodstream, or by direct invasion through the surrounding tissues, like in breast cancer," he says.
In the rare cases of heart cancer, symptoms tend to mimic other heart conditions: chest pain,palpitations, and shortness of breath, says Dr Xydas. Fatigue and weight loss are also common, and the symptoms could differ depending on which side of the body is affected: tumors on the right side can spread to the lungs and cause shortness of breath, while ones on the left could lead to stroke if they go to the brain, he adds.
24. The sentence “To understand why heart cancer is so rare, it's important to know just how cancer grows and spreads” should be placed at the beginning of（）.
A. Paragraph 2
B. Paragraph 3
C. Paragraph 4
D. Paragraph 5
25. It can be inferred from Paragraphs 3~4 that（）.
A. the mechanism of the heart has double-edged effects.
B. the heart is as vulnerable to disease as other parts of our body.
C. a cancerous tumor will form when mutated cells appear in our body.
D. the mechanism of the heart is impossible to develop cancer.
26.What's the author's purpose in writing the passage?
A. To explain why we seldom hear about heart cancer.
B. To introduce different causes of heart cancer.
C. To show how heart cancer develops.
D. To compare heart cancer with other kinds of cancers
24. [答案]B。解析:主旨题。根据题干关键词“grows”可定位到第三段。根据该段中的“As cells aregrowing and dividing, a mutation can occur, whether from genetic or environmental factors”及 “Those mutated cells startrapidly growing and dividing, ignoring signals designed to tell them to die. Eventually, they can form a canceroustumor”可知,在细胞增殖和分裂时，受遗传因素或环境因素的影响，细胞会出现变异;这些变异的细胞会加快速增殖和分裂，无视细胞凋亡信号,并最终形成癌性肿瘤。本段主要说明了癌症是如何产生和扩散.题干这句话可以概括该段的大意。故本题选B
25. [答案]A。解析:推断题。根据第四段中的“Ironically, the factors that make the heart so vulnerable to disease are also thought to make it less vulnerable to cancer" 及 Without being able to regenerate quickly ... the heart also might be better protected from environmental risk factors”可知,使心脏易生病的因素也被认为会使心脏不易患癌,由此可推断出,心脏机制具有双重效果。A项正确。根据第三、四段无法推断出B、C、D三项故排除。
26.[答案]A。解析:主旨题。通读全文可知,第一段和第二段通过与其他癌症进行对比,来说明心脏癌症罕见;第三段介绍了癌症产生和扩散的原因和方式;第四段说明了心脏机制的双重效果;第五段说明了诸如卡尼复合症等疾病增加了心脏肿瘤的风险;最后一段介绍了罕见心脏癌症的一些症状。综上所述，本文主要解释了心脏癌症罕见的原因且seldom是rare的同义转述，A项“解释我们为什么很少听到心脏癌症”最能概括本文主旨。故本题选A。
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