CARCINOGENESIS: ETIOLOGY AND PATHOGENESIS OF CANCER Carcinogenesis or oncogenesis or tumorigenesis means mechanism of induction of tumours (pathogenesis of cancer); agents which can induce tumours are called carcinogens (etiology of cancer). Since the time first ever carcinogen was identified, there has been ever-increasing list of agents implicated in etiology of cancer. There has been still greater accumulation in volumes of knowledge on pathogenesis of cancer, especially due to tremendous strides made in the field of molecular biology and genetics in recent times.          The subject of etiology and pathogenesis of cancer is discussed under the following 4 broad headings: A. Molecular pathogenesis of cancer (genes and cancer) B. Chemical carcinogens and chemical carcinogenesis C. Physical carcinogens and radiation carcinogenesis D. Biologic carcinogens and viral oncogenesis. A. MOLECULAR PATHOGENESIS OF CANCER (GENETIC MECHANISMS OF CANCER) Basic Concept of ...

  CHARACTERISTICS OF TUMOURS Majority of neoplasms can be categorised clinically and morphologically into benign and malignant on the basis of certain characteristics listed below. However, there are exceptions—a small proportion of tumours have some features suggesting innocent growth while other features point towards a more ominous behaviour. Therefore, it must be borne in mind that based characteristics of neoplasms,there is a wide variation in the degree of deviation from the normal in all the tumours. The characteristics of tumours are described under the following headings: I. Rate of growth II. Cancer phenotype and stem cells III. Clinical and gross features IV. Microscopic features V. Local invasion (Direct spread) VI. Metastasis (Distant spread). Based on these characteristics, contrasting features of benign and malignant tumours are summarised in Table and illustrated in Fig. I. RATE OF GROWTH The tumour cells generally proliferate more rapidly than the normal cells. In ...

NOMENCLATURE AND CLASSIFICATION INTRODUCTION . The term ‘neoplasia’ means new growth;the new growth produced is called ‘neoplasm’ or ‘tumour’.However, all ‘new growths’ are not neoplasms since examples of new growth of tissues and cells also exist in the processes of embryogenesis, regeneration and repair,hyperplasia and hormonal stimulation. The proliferation and maturation of cells in normal adults is controlled as a result of which some cells proliferate throughout life (labile cells),some have limited proliferation (stable cells), while others do not replicate (permanent cells). On the other hand, neoplastic cells lose control and regulation of replication and form an abnormal mass of tissue.    Therefore, satisfactory definition of a neoplasm or tumour is ‘a mass of tissue formed as a result of abnormal, excessive, uncoordinated, autonomous and purposeless proliferation of cells even after cessation of stimulus for growth which caused it’. The branch of science dealing wi...

EPIDEMIOLOGY AND PREDISPOSITION TO NEOPLASIA CANCER INCIDENCE The overall incidence of cancer in a population or a country is known by registration of all cancer cases (cancer registry)and by rate of death from cancer. Worldwide, it is estimated that about 20% of all deaths are cancer-related; in US, cancer is the second most common cause of deaths, next to heart disease. There have been changing patterns in incidence of cancers in both the sexes and in different geographic locations as outlined below. Table shows worldwide incidence (in descending order) of different forms of cancer in men,women, and children. As evident from the Table, some types of cancers are more common in India while others are commoner in the Western populations since etiologic factors are different.            In general, most common cancers in the developed and developing countries are as under: • Developed world : lung, breast, prostate and colorectal. • Developing world : liver, ...