Impact of Alcian blue and periodic acid Schiff expression on the prognosis of gastric signet ring cell carcinoma

BACKGROUND The Alcian blue (AB) and periodic acid Schiff (PAS) stains are representative mucus markers in gastric signet ring cell carcinoma (SRCC). They are low-cost special staining methods used to detect acidic mucus and neutral mucus, respectively. However, the clinical importance of the special combined AB and PAS stain is unclear. AIM To investigate AB expression, PAS expression and the AB-to-PAS (A/P) ratio in gastric SRCC patients and to assess patient prognosis. METHODS Paraffin-embedded sections from 83 patients with gastric SRCC were stained with AB and PAS, and signet ring cell positivity was assessed quantitatively. Immunohistochemical staining for Ki67, protein 53 (P53) and human epidermal growth factor receptor 2 (HER2) was performed simultaneously. The cancer-specific survival (CSS) rate was estimated via Kaplan-Meier analysis. Cox proportional hazards models were used for univariate and multivariate survival analyses. RESULTS Kaplan-Meier survival analysis revealed that the 3-year CSS rate was significantly greater in the high-PAS-expression subgroup than in the low-PAS-expression subgroup (P < 0.001). The 3-year CSS rate in the A/P ≤ 0.5 group was significantly greater than that in the A/P > 0.5 group (P = 0.042). Univariate Cox regression analysis revealed that the factors affecting prognosis included tumor diameter, lymph node metastasis, vessel carcinoma embolus, tumor stage, the A/P ratio and the expression of Ki67, P53 and the PAS. Cox multivariate regression analysis confirmed that low PAS expression [hazard ratio (HR) = 3.809, 95% confidence interval (CI): 1.563-9.283, P = 0.003] and large tumor diameter (HR = 2.761, 95%CI: 1.086-7.020, P = 0.033) were independent risk factors for poor prognosis. CONCLUSION A/P > 0.5 is potentially a risk factor for prognosis, and low PAS expression is an independent risk factor in the prognosis of gastric SRCC. PAS expression and the A/P ratio could help in predicting the clinical prognosis of patients with SRCC.