癌是由癌细胞组成的。从正常细胞变成癌细胞,总有一定的外部诱因和内因,而且有一个演变过程。细胞的不典型增生就是癌前期病变。如果我们能在癌前期病变阶段就发现并及时治疗,那么就可能免除一场癌肿的灾难。经过长期观察发现,某些慢性疾病可以发展成癌,医学上一般把这类疾病称为癌前期疾病。认识和防治这些疾病,也是预防癌肿的重要环节。这些癌前期疾病主要有: Cancer is composed of cancer cells. From normal cells into cancer cells, there is always some external incentives and internal causes, but also an evolutionary process. Atypical hyperplasia of cells is precancerous lesions. If we can find and promptly treat at the stage of precancerous lesions, then it is possible to get rid of a cancer of the disaster. After long-term observation found that some chronic diseases can develop into cancer, such diseases are generally referred to as pre-cancerous diseases in medicine. Recognize and prevent these diseases, but also an important part of prevention of cancer. These precancerous diseases are mainly: