Cancer is one deadly disease which takes lives of many people throughout the world every year. It is the most common cause of death after cardiovascular disease. Cancer occurs due to uncontrolled and rapid cell division of malignant cells. Cell division is a controlled process. Usually, an animal cell divides for a specific number of times which is called its Hayflick’s limit. This phenomenon is genetically controlled.
- A defect in DNA due to mutation or activation of the oncogene, or deactivation of tumor suppressor gene, the genetic control is lost and cells divide continuously beyond the Hayflick’s limit resulting in a mass of useless cells, known as tumor. The tumor-forming cells are called malignant cells. These are also known as neoplastic cells or cancer cells.
- A mass of useless or dysfunctional cells resulting from rapid uncontrolled division of malignant cells is known as a tumor. Some of the common and prominent types of tumors are discussed below:
- The benign and noninvasive tumor is formed due to the rapid uncontrolled division of neoplastic cells, restricted at the site of origin. The division stops after sometime.
- When rapid uncontrolled cell division of neoplastic cells continue, and the tumor spreads to other parts of the body and forms secondary tumors, they are known as malignant tumors and the condition is commonly called cancer.
A cancerous tumor first grows slowly and no symptoms are noticed at this stage. This stage is called latent stage. After the latent period tumor grew rapidly, the cells of which attack the neighboring normal cells. These cells compete with normal cells for nutrients. When the number of cancer cells increases to a great extent, they draw all the nutrition. As a result, normal cells suffer from lack of it and death ensures. Still later, tumor cells can break away and spread to other parts of the body vialymph or blood causing secondary tumors or metastases, where the attack new tissues. Cancerous cells interfere with the body’s normal functioning and cause the death of the victim.
Types of Cancer
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- Carcinoma: the Malignant growth of epithelial cells is the most common type of cancer. About 85% of tumors are carcinomas. Carcinoma includes skin cancer, breast cancer in females, cervical cancer, brain cancer, stomach cancer, lung cancer etc. The cancerous growth of melanocytes of skin is known as melanoma.
- Sarcoma: the Malignant growth of connective tissue which includes the cancer of bones (osteoma), cartilages, tendons, muscles ligaments and adipose tissue. It is not common in humans.
- Lymphoma: Malignancy of lymph nodes. For example, Hodgkin’s disease characterized by chronic enhancement of the production of lymphocytes by lymph nodes and spleens.
- Leukemia: Malignancy ofhematopoietic cells of red bone marrow. This results in the formation of excessive WBC’s in the bone marrow and lymph nodes.
The growth of Normal Cell and Malignant Cell
In a normal cell growth is slow in the beginning and then it becomes rapid, before slowing down and remaining stationary, and finally dies. Cancerous cells grow very rapidly from the beginning and are immortal.