Abstract: Wang Ying, Kang Xiaojing, ZhaoJuan, Liang Junqin, Zhang Dezhi, Chai Li, Wang Peng, Wang Weijia Department of Dermatology and Venereology, People′s Hospital of Xinjiang Uygur Autonomous Region, Urumqi 830001, China Corresponding author: Kang Xiaojing, Email: drkangxj666@163.com 【Abstract】 Objective To detect the level of 5-hydroxymethyl-cytosine（5-hmc）in melanoma tissues, and to analyze the correlation between 5-hmc and the invasion, metastasis and prognosis of melanoma. Methods A streptavidin-peroxidase immunohistochemical method was used to detect the level of 5-hmc in 67 melanoma tissues and 20 pigmented nevi tissues. Univariate and multivariate analyses were performed with the Cox′s proportional hazards regression model to analyze the correlation between the of 5-hmc and the prognosis of melanoma. Results The rate of 5-hmc was significantly lower in melanoma tissues than in pigmented nevus tissues （40.30%［27/67］ vs. 75%［15/20］, χ2 = 7.428, P = 0.006）. According to American Joint Committee on Cancer （AJCC） TNM staging system, the level of 5-hmc was significantly lower in the stage Ⅳmelanoma tissues than in the stage Ⅱ and stage Ⅲ melanoma tissues （χ2 = 4.416, P = 0.036）. Patients with lymph node metastasis showed significantly lower of 5-hmc compared with those without lymph node metastasis （χ2 = 5.902, P = 0.015）, and the level of 5-hmc significantly decreased along with the increase of Clark grade （χ2 = 4.828, P = 0.028）. There were no significant differences in the level of 5-hmc between patients of different ages, genders or nationalities （P > 0.05）. Multivariate Cox regression analysis showed that distant lymph node metastasis （HR: 2.67, 95% CI: 1.22 - 5.84）, not receiving surgical resection （HR: 0.41, 95% CI: 0.18 - 0.95）, and low of 5-hmc（HR: 3.54, 95% CI: 1.09 - 11.43）were independent risk factors for poor prognosis of melanoma. Conclusion 5-Hmc may participate in the invasion and metastasis of melanoma, and be associated with the prognosis of melanoma.

Key words: 5-Methylcytosine, Nevi and melanomas, Biological marker, Prognosis, Neoplasm metastasis