4 DISCUSSION
Vocal cord leukoplakia has the potential for malignant transformation.7 Laryngoscopy is the main means to diagnose vocal cord leukoplakia. The accurate diagnosis of the malignant possibility of vocal cord leukoplakia is closely related to the clinical experience of laryngologists. Previous research showed that the NBI laryngoscopy could help to improve the diagnostic accuracy by observing the morphology of microvessels on the mucosal surface.8 However, since the NBI laryngoscopy has not been fully popularized clinically, making accurate judgments also require training.9 Most laryngologists still observe vocal cord leukoplakia by WLI laryngoscopy. Therefore, it is of greater clinical significance to improve the diagnostic accuracy of vocal cord leukoplakia under WLI laryngoscopy.
Although the gross appearance of vocal cord leukoplakia with different pathological properties is sometimes approximately similar, some researchers have tried to use WLI laryngoscopy for the scoring and classification of vocal cord leukoplakia to evaluate the possibility of malignancy and guide treatment. Representative scoring systems are the leukoplakia scoring system proposed by Fang et al. 4 and the classification proposed by Zhanget al. 5 Fang et al. results showed that age, lesion heterogeneity, and hyperemia were independent factors for predicting malignant vocal cord leukoplakia. Afterward, the formula (score = 0.060 × age + 2.609 × texture + 1.307 × hyperemia) was proposed on the basis of the regression coefficient. This score is of some clinical value for predicting the malignancy of vocal cord leukoplakia (AUC = 0.86). Zhang et al. classified vocal cord leukoplakia into three types according to roughness. Further studies by this team showed that the classification of vocal cord leukoplakia into the low-risk and high-risk groups had a certain auxiliary effect (AUC = 0.863) and helped to guide the choice of clinical treatment.10,11 In this classification system, type I mostly suggests low-risk leukoplakia, whereas type III mainly suggests high-risk vocal cord leukoplakia. However, the differential diagnosis of type II leukoplakia is not accurate, mainly because this classification was only based on texture and ignored other factors. Some studies have shown that under WLI laryngoscopy, the existence of hyperemia12 and vascular stippling13 are closely related to atypical hyperplasia and malignancy. Although Fang’s scoring system considered texture and hyperemia, it is not widely applied in clinical practice. The main reason is that the formula of this scoring method is difficult to remember, and in addition, there is also a lack of consideration of other factors associated with malignant vocal cord leukoplakia (such as color, size, and symmetry), which leads to an average diagnostic efficiency (sensitivity 80.4%, specificity 81.5%).4
In order to improve the accuracy and objectivity of the evaluation of the nature of vocal cord leukoplakia by laryngoscopy, all morphological factors associated with benign and malignant leukoplakia were included in this study by referring to the grading method of reflux finding score (RFS) in the diagnosis of laryngopharyngeal reflux.14Scores were assigned according to the regression coefficient. The regression analysis showed that hyperemia was the most important factor. For easy memorization, 4 points were assigned to hyperemia, 2 points to the involvement of anterior commissure and thickness, and 1 point was assigned to size and texture. The final range of the score was 0–10 points. This scoring system showed a very strong consistency between the two laryngologists (kappa = 0.809). The AUC of this LFS for the diagnosis of benign and malignant vocal cord leukoplakia was 0.946, which was higher than that of the Fang score (AUC=0.880) and Zhang classification (AUC=0.742). The reference cutoff point for diagnosing malignant vocal cord leukoplakia was ≥6 points. The sensitivity, specificity, and accuracy of this scoring method were 93.8%, 83.6%, and 86.0%, respectively. It can be seen from this study that hyperemia of vocal cord leukoplakia is the most important predictor of malignancy (it has a maximum weight of 4 points in the scoring system); thus, this feature should be a focus of evaluation during laryngoscopy. This characteristic of WLI laryngoscopy that corresponds to the performance of NBI laryngoscopy is tortuous dilated microvessels, which is the main observation point of NBI laryngoscopy used to judge the nature of the lesions.15 To accurately judge whether vocal cord leukoplakia is hyperemic, it is critical to observe as close as possible to the vocal cord surface during laryngoscopy and pay attention to the edge of the leukoplakia. In addition, the involvement of the anterior commissure is closely related to the malignant transformation of vocal cord leukoplakia (assignment of 2 points), which has not been reported in other studies. It is necessary to report the relationship between vocal cord leukoplakia and the anterior commissure to provide accurate clinical information for subsequent minimally invasive surgical treatment.