Up-regulated ODC expression has been reported in various solid cancers, including skin cancer,19 gastric cancer,20 neuroblastoma,21 and colon cancer.22 In the present study, we explored the expression pattern of ODC in ESCC tissues by immunohistochemistry (IHC). ODC immunostaining was observed in both nucleus and cytoplasm (Fig. 1). Among 110 evaluable ESCC cases, positive staining for ODC was observed in 93.6% of the tissues (103/110). In esophagitis and normal adjacent tissues (NAT), ODC positive staining was 60.0% (9/15) and 52.6% (10/19), respectively (Supplementary Fig. 1). Quantitative analysis showed that the ODC immunostaining integrative optical density (IOD) value was 2255 ± 115 for ESCC, which was significantly higher than the value for esophagitis (1187 ± 236, p < 0.01) or NAT (888 ± 140, p < 0.01; Fig. 1a). The correlations between clinicopathological features and ODC expression in the primary ESCC were determined (Supplementary Table 2). The ODC expression level in ESCC was significantly correlated with lymph node metastasis status (p = 0.02, Fig. 1b) and clinical stage (p = 0.02, Fig. 1c), but was not associated with age, gender, or tumor histological grade.Fig. 1ODC expression is up-regulated in ESCC. a The ODC immunohistochemical IOD value is significantly higher in ESCC compared to esophagitis or NAT. The ODC protein expression level in ESCC is significantly correlated with b status of lymph node metastasis and c clinical stage. Significant differences were determined using the Student’s t test