Introduction

Cancer is a complex family of diseases that usually begins with carcinogenesis, in which abnormal cells divide or develop wildly by not following the regular path of cell division and likewise can invade nearby tissues. Cancer cells demonstrate transformations in metabolism, which is frequently more anaerobic than normal and probably can tolerate hypoxic surroundings. The remarkable variability of the disease, at all levels, is the major challenge for cancer medicine. Six biological abilities gained during the multi-stage advances of human tumors are the maintenance of proliferative signaling, the prevention of growth suppressors, cell death resistance, replicative immortality allowance, angiogenesis induction, invasion, and metastasis activation. In this chapter, we discuss the features of cancer cells and the epidemiology of cancer for better understanding.