Most common neoplasm due to radiaton:

Ans: d (Leukemia)Ref: Harsh Mohan, 5th ed pg. 222,Radiation carcinogenesis:The causative agents are UV rays and ionizing radiationMalignancy can appeareven after a latent period of 10-20yrs.UVraysFrom sunlight, UVlamp, welders arcsCause various skin cancersMajor mech is induction of mutation Most important biochemical effect is the formation of pyramidine dimers in DNA.Ionizing radiationInclude Xrays, alpha, beta, gamma rays, radioisotopesMost common malignancy is all leukaemias except CMLOthers include malignancies of thyroid, breast, skin, ovary, uterus, lung etc.Chances are more with neutrons & alpha rays - due to more LET (linear energy transfer)MechanismBy directly altering the cellular DNA By dislodging ions from water and other molecules resulting in the formation of highly active free radicals.