Tumors can be benign or malignant. Benign tumors grow slowly and do not spread. When tumors are malignant, they are termed as ‘cancer’ and can cause harm including “death”. The ‘malignant’ nature of cancer is due to its locally invasive nature (tumor invading the surrounding cells) and metastatic nature (tumor invading the other tissues in the body).
The original tumor is called as the primary tumor. The cells of the primary tumor travel through the circulatory system and lymphatic system to form new tumors called as secondary tumors in other organs.
Occurance of Cancer in different groups (Epidemiology)
Prevalence of cancer in different regions of the world varies depending on the type of cancer occurring in that particular region. Epidemiological studies suggest that breast cancer and prostrate cancer are common in the developed countries of the world, whereas cervical cancer and stomach cancer occur more frequently in developing countries. Lung cancers seem to have high incidence in both developed and developing countries.
The differences in the prevalence of cancer in different regions of the world can be explained through heredity, medical practices, lifestyle changes and environmental exposures like different diets, tobacco and pesticides. Studies suggest that the incidence of colon cancer is seen more in people who are obese.
Studies across the populations suggest that men are more to prone to develop colorectal cancer than women. Obesity has shown to increase the prevalence of breast cancer in postmenopausal women by 30–50%. Other kinds of cancer related to obesity include endometrial, pancreatic, kidney, liver cancer, gall bladder etc.
Studies from developed countries show that cancer is exceeding cardiovascular diseases and has become a major cause of death when compared to underdeveloped countries, where infectious diseases is the major cause of death.
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