My Dad's RO also had said that PET is not a conclusive test, even if something lights up, they cannot take it as Cancer. It has to be always followed up with Biopsy and he also added that very rarely even Biospy goes wrong!

Father; 67 yrs; RIP: 2012/05/26

TX:SCC pT2N1M0G2;Glossectomy+SND+CCRT(59.3Gy+6xCis.)[2009]
TX:Nodal Mets; 3xDCF[2011/05/05]
TX: RND + PMMC Flap[2011/07/11]
DX:SCC PNI+ECE
TX:Re-RT 60Gy[2011/09/21]
TX:Gefitinib 250mg[2011/12/18]