(a) In normal cells, growth and differentiation is highly controlled and regulated (contact inhibition). The cancerous cells have lost the property of contact inhibition,hence continue to divide giving rise to masses of cells (tumors).
(b) The benign tumor remains confined in the organ affected as it is enclosed in a connective tissue sheath and does not enter themetastatic stage.
(c) Cancer may be caused due to carcinogens which are physical(radiations), chemicals (Nicotine, Aflatoxin, Cadmium oxide, Asbestos) and biological (viral oncogens)
(d) Surgery, radiothera]py, Chemotherapy