Fig. 1From: Immunohistochemical prognostic markers of esophageal squamous cell carcinoma: a systematic reviewFlowchart of study selection for this systematic review on immunohistochemical prognostic markers of esophageal squamous cell carcinoma. ELISA enzyme-linked immunosorbent assay, PCR polymerase chain reaction, lncRNA long non-coding RNABack to article page