The first peptide mass fingerprinting data on CA125 was described in 2003 where 16 masses, corresponding to peptides of a 1148 amino acid form of CA125 from HeLa cells, were detected [12]. This enabled the identification of CA125 as a binding protein of galectin-1. In a later study, Jankovic et al. identified an approximately 200 kDa form of CA125 in first trimester human placental extract based on 36 experimentally detected masses [51]. Similarly, Milutinovic et al. reported identification of 46 masses that matched to CA125 in human amniotic fluid [52].