(a)What makes some viruses cause cancer in humans?
(b)How do benign tumours turn malignant?How do the latter harm the human body?
(a)Cancer-causing viruses have genes called viral oncogenes.The normal proto-oncognes get activated into oncogenes by some viruses and lead to oncogenic transformation of cells.
(b)A benign tumor may turn malignant if it is not removed as soon as it is noticed.The cancerous cells are carried by blood or lymph to other parts of the body where they spread secondary cancers or metastasis.A malignant tumour is not self-limited in its growth, is capable of spreading to distant tissues.A benign tumour has none of those properties.