ERBB2 and gastric neoplasm: To evaluate the expression of both ErbB2 sialylated glycoforms in GC, the molecular proximity between ErbB2 and SLea and α2,6NeuAc was detected through in situ brightfield Proximity Ligation Assay (PLA) in gastric tumor tissues, using the CA 19-9 mAb and the Sambucus nigra agglutinin (SNA), respectively.