Cancer is a group of diseases characterized by the uncontrolled and abnormal growth of cells in the body, where these cells lose their normal regulation and ability to die at the right time, leading to the formation of masses or tumors that may be benign or malignant. The dangerous aspect of malignant tumors is their ability to invade nearby tissues and spread to other parts of the body through a process known as metastasis. The causes of cancer are complex and involve multiple factors, including genetic factors, where inherited mutations can increase a person’s susceptibility to the disease. Environmental factors also play a major role, such as exposure to pollution, harmful chemicals, and radiation. Smoking is one of the leading causes of many types of cancer, especially lung cancer, due to the presence of toxic and carcinogenic substances that damage body cells. In addition, an unhealthy diet low in fruits and vegetables and high in processed foods and saturated fats can increase the risk of developing cancer. Lack of physical activity and obesity are also important risk factors. Excessive exposure to ultraviolet radiation from the sun without protection can lead to skin cancer. Certain viral infections, such as human papillomavirus (HPV) and hepatitis viruses, are also linked to the development of cancer by causing cellular changes. Despite its seriousness, cancer can often be prevented to a significant extent through healthy lifestyle choices. Quitting smoking and avoiding secondhand smoke are essential preventive steps. Maintaining a balanced diet rich in fruits, vegetables, and antioxidants helps protect cells from damage. Regular physical activity is important for maintaining a healthy weight and strengthening the immune system. It is also recommended to limit exposure to direct sunlight and use sunscreen when necessary. Regular medical check-ups and early screening are crucial, as early detection greatly increases the chances of successful treatment and recovery. Vaccination against certain cancer-related viruses, such as HPV, also helps reduce risk. Managing stress and maintaining good mental health are important as well, since chronic stress may negatively affect the immune system. In conclusion, cancer is a serious but largely preventable disease, and awareness, prevention, and early diagnosis play a key role in reducing its impact and improving quality of life.