Method Selection And Clinical Study Of Laser Treatment For Medium-sized Melanocytic Nevus

Objective:Detecting the effectiveness and practicability of fractional CO₂ laser combined with Nd:YAG laser in the treatment of Medium-sized melanocytic nevus.Methods:This study included 20 patients who met the selected criteria with the Medium-sized melanocytic nevus from October 2018 to December 2020.all patients were treated with fractional CO₂laser and1064 nm Q-switched Nd:YAG laser with a treatment interval>3months.The number of combined treatment was determined the situation of lesion,then treated with 1064 nm Q-switched Nd:YAG laser only.The treatment interval>2 months.All laser wounds were treated with MEBO wet wounds.All patients took photos of the treatment area before each treatment.Efficacy evaluation indexes:1.Two clinicians not related to the experiment made an objective effectiveness evaluation by comparing the photos before and after treatment.2.Evaluation of patients’satisfaction before and after treatment.3.Lab color model was used to evaluate the color of lesions before and after treatment.4.The histological changes of lseions were observed by HE staining and immunohistochemical double staining（Dct,Tyr）.5.All data were statistically processed using SPSS 24.0software.The measurement data were expressed as mean standard deviation,and the count data were analyzed by T test.p<0.05 was considered statistically significant.Use Pearson correlation coefficient to analyse correlation.Results:1.Among the 20 patients,9cases（45%）were male,and the effective rate was 50%.Among the 11（55%）female patients,the effective rate was 63.5%,and there was no significant difference between men and women（P>0.05）.The age of treatment beginning was 6.13±6.87 years old（7mo-24y）.There were 10 patients（50%）with younger age（<4 years old）,and the effective rate was 40%.10 patients with older age（≥4 years old）,and the effective rate was 75%.There was a significant difference between younger and older patients（P<0.05）.The Average area of lesions was 12.51±17.86（2.25-48 cm2）.Patients with small lesion area（<4 cm²）,the effective rate was 65%;Patients with large lesion area（≥4 cm²）,the effective rate was 50%,There was no significant difference in the effectiveness of lesion area（P>0.05）.The average number of treatments was 5.25±3.63（1-10times）.2.The observer evaluated the efficacy of 20 patients who received once treatment of fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser.The average score was 2.28±1.11,and the effective rate is 35%.There were 16 cases received twice treatment of fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser.The average observer score was 2.44±1.16,and the effective rate was 43%.There were 8 cases received thrice treatment of fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser.The average observer score was 2.50±0.89,and the effective rate was 37.5%.There were 5 cases received thrice treatment of fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser and once of 1064 nm Q-switched Nd:YAG laser.The average observer score was 3.30±0.82,and the effective rate was 80%.The average observer score of integral treatment of 20 patients is 3.03±1.35,and the effective rate is57.5%.Patients’evaluation:the average score was 3.05±1.82 and the effective rate was 65%.After the treatment 2 cases（10%）developed scars,1 cases（5%）were decolored,3 cases（15%）the short-term effect is good but the recurrence is obvious.3.Lab color model evaluation:12 cases（60%）with a change rate(L_变化率)which is the darkness change of the lesion more than50%.The average change rate is 56.68±24.26%.12 cases（60%）with a lesion clearance rate more than 50%.The average clearance rate is56.68±24.26%.The Pearson correlation coefficient between subjective evaluation and objective evaluation of Lab color pattern was calculated.It was concluded that the observer score was significantly correlated with the darkness change rate and the clearance rate（P<0.05）.The patient satisfaction score was significantly correlated with the darkness change rate and the clearance rate（P<0.05）.4.Pathological section observation:The HE staining after treatment showed that the nevus nests in the epidermis and dermis were significantly reduced,the nevus’nests were obviously denatured in the epidermis,the melanocytes were denatured in the stratum basale and the scattered nevus cells in the dermis.It can be observed that the collagen fibers in the papillary laye are slightly vitreous after laser treatment,but the structure of each layer of tissue remains relatively complete.The immunohistochemical double staining（Dct,Tyr）showed:Melanocyte stem cells were not observed in the nevus’nests in the epidermis and dermis,but only in the bulge-secondary hair germ and dermal papilla.Conclusion:1.Fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser treatment of medium-sized melanocytic nevus is effective.And the effect is related to the number of treatments.The more times of treatment,the greater degree of improvement with the same patients.2.The effectiveness of Fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser on medium-sized melanocytic nevus is related to the age of the patients.Patients whom age of one to three have less accurate efficacy.3.The effectiveness of Fractional CO₂laser combined with 1064 nm Q-switched Nd:YAG laser on medium-sized melanocytic nevus is independent of the patient’s gender and lesion size.