Tumour virology

Abstract

In its original sense the word tumour described any abnormal swelling in an individual, but its use is now restricted to pathological conditions caused by the excessive and apparently purposeless growth of cells — often with harmful effects. Tumours may arise from almost any cell in the body — an interesting exception being the adult neurone — and often show a resemblance to normal types of cell and tissue. Tumours vary widely in their rates of growth and in the ability of their cells to invade surrounding tissues and to spread via the blood stream and lymphatics to form distant independent growths — metastases. The cells of benign tumours remain localized at their site of origin and are usually slow-growing, closely resembling normal cells in most respects. Malignant tumours contain cells with pronounced invasive properties and with the capability of producing metastases. Common types of malignant tumours include the carcinomas (tumours of epithelial tissues) and the sarcomas (tumours of connective tissue, cartilage and bone).