Abstract: Objective To investigate whether ENOX2 protein can be detected in the serum of patients with orbital tumors, and observe whether the expression of the protein is tissue specificity, and explore the relationship between the expression characteristics of ENOX2 protein and the types of ocular tumors. Design Prospective case series. Participants 43 patients with orbital mass in Beijing Tongren Hospital from November 2015 to April 2016. Methods Serum of enrolled patients was collected. The enrolled patients underwent tumor resection and postoperative pathological examination. The ENOX2 protein detection was carried out using 2D electrophoresis. And the accuracy of ENOX2 protein detection was evaluated based on pathological diagnosis. Main Outcome Measures The detection results and molecular characteristics of ENOX2 protein in patient's serum. Results The final pathological diagnosis showed that there are 27 cases patients of benign tumor, 16 cases of malignant tumor (1 case of basal cell carcinoma, 3 cases of lymphoma, 6 cases of meibomian adenocarcinoma, 2 cases of squamous cell carcinoma, 3 cases of retinoblastoma, 1 case of melanoma). Based on the verification of ENOX2 protein results and pathological diagnosis results, we found and the ENOX2 positive rate of orbital malignancy tumor was 94% (3/3 in limphoma, 100%; 2/2 in squamous cell carcinoma, 100%; 6/6 in meibomian adenocarcinoma, 100%; 2/3 in retinoblastoma, 66.70%). The molecular features of ENOX2 protein in meibomian adenocarcinoma were discovered for the first time (molecular weight is 37 kDa, isoelectric point is 4.9). Conclusion ENOX2 protein can be used as a potential serum marker for the early diagnosis of orbital tumors and has certain specificity. (Ophthalmol CHN, 2020, 29: 401-405)

Key words: orbital tumor, biomarker, nicotinamide adenine dinucleotide oxidase disulfide exchange protein 2