Cancer represents a group of diseases which involve abnormal cell growth that could spread and invade different parts of the body. The cells start dividing uncontrollably and invading and destroying normal body tissue. Cancer can easily spread throughout the whole body, making it the second cause of death worldwide.
In most cases, oncogene activation and/or tumor suppressor gene deactivation results in uncontrolled cell cycle progression and inactivation of apoptotic mechanisms. Malignant malignancies, as opposed to benign tumors, develop metastasis, which is caused in part by the down-regulation of cell adhesion receptors required for tissue-specific cell-cell attachment.
Only malignant tumors are legitimately referred to as cancers, and cancer is harmful because of their capacity to penetrate and metastastize. Whereas benign tumors may normally be removed surgically, malignant tumors are frequently resistant to such limited therapies due to their ability to spread to distant body regions.
Tumors are classed as benign or malignant based on the kind of cell that gives birth to them. Most malignancies are classified into one of three types: carcinomas, sarcomas, and leukemias or lymphomas. Carcinomas are epithelial cell tumors that account for about 90% of all human cancers. Sarcomas are solid tumors of connective tissues such as muscle, bone, cartilage, and fibrous tissue that are uncommon in humans.
Leukemias and lymphomas, which account for around 8% of all human cancers, start from blood-forming cells and immune system cells, respectively. Tumors are further categorized based on their origin tissue (for example, lung or breast carcinomas) and the kind of cell involved. Fibrosarcomas, for example, develop from fibroblasts, and erythroid leukemias from erythrocyte progenitors (red blood cells).
One of the most significant early findings concerning cancer was that its prevalence varied between populations. In 1775, for example, an unusually high prevalence of scrotal cancer was reported among adults who worked as chimney sweeps as youngsters.
Lung cancer was found at disturbingly high rates among pitchblende miners in Germany in the mid-1800s. By the end of the nineteenth century, several physicians believed that taking snuff and cigars was linked to malignancies of the mouth and throat.
There is a strong cause-effect relationship between environment and cancer. Studies show that most deaths by cancer happen in poor, underdeveloped countries and in low and middle-income classes. The inability of humans to treat their bodies correctly can have deadly effects.
In addition, the lack of hospitals and well-trained medical staff is another problem in the less developed countries. As studies show, there are more chances to successfully treat cancer and survive in the most developed countries than in the underdeveloped ones.
Based on information obtained from “Our world in data", in 2009, the 5 years survival rate of Lung cancer was at approximately 30%, while in Bulgaria and Mongolia it was only 7%. The 5 years survival rate of Breast cancer is over 80% in North America, Europe, and Oceania, while in Jordan only 43%. The lowest survival rate of Liver cancer in 2009 was recorded in Romania with 2.3%, while the survival rate in Japan for the same disease was almost 27%.