Using the same MS-based approach on a fresh-frozen tissue section of an ErbB2-positive gastric adenocarcinoma, the N124 glycosylation site was successfully validated and found to be occupied by Man9 glycan species, in agreement with observations made for GC cell line-derived ErbB2 (Fig. S4, Table S2). This evidence concerns the gene MAN1A1 and gastric adenocarcinoma.