'Knudson's two-hit' hypothesis is associated with-

Harshmohan textbook of pathology 7th edition. Familial retinoblastoma comprises 40% of cases and may be bilateral . In this cases all somatic cells inherit one mutant RBgene from a carrier parent. Later during life the other mutational event of 2nd allele affecting the somatic cells occurs. This forms the basis of two hot hypothesis given by Knudson in 1971..