Appearance of synchronus and metachronus tumour in upper aerodigestive tract.
Field cancerisation could be due to mechanism underlying development of multiple primary tumour: Presence of P53 mutant and elevated IL-4 receptor in distant normal mucosa suggest that these underlying changes could develop multiple primary
It could be due t multiple primary sharing same clonal origin. Same clonal origin develop deep and then migrate within mucosa and develop distinct genetic alteration later. In female X-chromosome inactivation leads to clonal origin of multiple tumour.