Viruses and Cancer

Viruses and Cancer - Cell division is a normal process in multicellular organisms. Growth and repair (replacement of dead cells) take place as a result of cell division (mitosis). Except for cells like the liver and brain cells, which rarely divide in the mature adult, most cells undergo frequent division. Sometimes, however, cell division becomes very rapid and uncontrolled, leading to cancer.

It should be clearly understood that rapid growth means a high rate of cell division for a particular cell type. It is possible for perfectly normal cells, e. g. the blood forming cells, to have a higher rate of division than some cancerous cells.

Cells which undergo rapid, abnormal and uncontrolled growth at the cost of remaining cells are called neoplastic cells. The growths resulting from the division of such cells are called neoplastic growth or tumour. Tumours are commonly classified as benign and, malignant. Abnormal and persistent cell division that remains localized at the spot of origin results in the so called benign tumours.

It should be noted, however, that benign tumours can sometimes be fatal, Ex. brain tumours that cause pressure on vital centres. benign tumours usually contain well differentiated cells. Tumour cells may be carried by the blood stream, or the lymphatic system, or by direct penetration to other parts of the body, where they may induce secondary(metastaiic) tumours.

Such invasive cancers ultimately result in the death of the organism and are therefore said to be, malignant. Malignant tumours usually contain undifferentiated cells, often with large nuclei and nucleoli.