Recessive oncogene, which has been originally proposed for the retinoblastoma susceptibility gene, is linked to the development of cancer by missing its gene function followed by the loss of normal allele (often observed as a loss of heterozygosity of neighbouring heteromorphic loci). Recent studies on the loss of heterozygosity in cancers indicate that mutations of such genes are relatively common in human cancers, and play a significant role in the dedifferentiation, progression and evolution of cancers as well as the initiative role. Such initiative and cooperative role of recessive oncogene opened a new field relating to the research on the genetic origin of cancer, evolutional implications of cancer development, and molecular diagnosis for cancer prognosis.