据统计,全世界每年至少有500万人死于癌症,居人类死亡率的第二位。癌症之所以可伯,是因为人们尚未完全认识它,所以也就不能有效地遏止它猖獗的生长。但也有不少人患癌症多年,最后,癌竟完全消失了,实验肿瘤自发性退变也不乏其例。此外,在相同的生活环境下,患癌的只是极少数,绝大多数人并不得癌。这表明机体对肿瘤有着强大的防御机能,只有当这种机能缺损时肿瘤细胞才能乘虚而生,在机体一系列的防御机能中,免疫监视机能最为重要,而担负这一重任的却是一个微小的不为人们所重视的淋巴器宫——胸腺。胸腺位于胸腔的前纵膈内,骑跨在心脏的前上方。其主要细胞成份是胸腺细胞和上皮性网状细胞,后者可以分泌胸腺激素,还可提供胸腺细胞产生和成熟的微环 According to statistics, at least 5 million people in the world die of cancer each year, ranking second in human mortality. The reason why cancer can be achieved is because people do not fully understand it, and therefore cannot effectively curb its growth. However, many people have been suffering from cancer for many years. In the end, the cancer has completely disappeared. There is no lack of examples of spontaneous degeneration of experimental tumors. In addition, in the same living environment, only a very small number of people suffering from cancer, the vast majority of people can not be cancerous. This shows that the body has a strong defensive ability against the tumor. Only when this function is lost can the tumor cells take over. In a series of defensive functions of the body, immunity monitoring function is the most important, but it is a tiny burden to carry this responsibility. The lymphatic palace, which is not valued by people, is the thymus. The thymus is located in the anterior mediastinum of the thorax, riding across the front of the heart. Its main cellular components are thymocytes and epithelial reticular cells, which can secrete thymic hormones, and can also provide thymus cells that produce and mature microrings.