The more striking differences are evident in the significant IgA increase in the predetermined sites of stomach in the patients with gastric cancer compared with tumor-free patients (Optical Density median, IQR: antrum 0.868, 0.578–0.945 vs. 0.176, 0.129–0.867; p = NS; angular portion 0.802, 0.637–1.051 vs. 0.275, 0.135–0.945, p = NS; corpus 0.836, 0.688–1.039 vs. 0.413, 0.134–0.737, p = 0.006; fundus 0.772, 0.668–1.115 vs. 0.267, 0.160–0.675, p = NS). Here, CD79A is linked to neoplasm.