Moderate Laryngeal Dysplasia in the Context of Classification Systems and Clinical Decision Making

Determining the prognosis of vocal fold leukoplakia remains challenging. The 2017 WHO Classification of Head and Neck Tumors proposed a two-tier grading system for classifying laryngeal precursor lesions. This resulted in the upstaging of "moderate dysplasia" to "high-grade dysplasia." The aim of this study was to retrospectively analyze the rates of malignant transformation in relation to the grade of dysplasia.

Totally, 392 patients who underwent at least one microlaryngoscopy with biopsy for laryngeal leukoplakia were included in this study. The rate and time to malignant transformation were analyzed according to the histopathological diagnosis and the localization of the leukoplakia.

Malignant transformation rates (defined as de novo occurrence of an invasive carcinoma) were low for hyperkeratosis or parakeratosis and mild dysplasia, but comparably high for moderate dysplasia, severe dysplasia, and carcinoma in situ (CIS) (6% vs. 9% vs. 41% vs. 43% vs. 55%). The time between first biopsy and malignant transformation varied widely (0.1-10.8 years) and did not show a significant dependence on the initial histopathological diagnosis.

Based on the observed malignant transformation rates, the data support classifying moderate dysplasia into the "high-grade" dysplasia group, in line with the fourth WHO classification from 2017. This implies that the clinical management of moderate dysplasia should align with that of severe dysplasia and CIS, involving histologically controlled resection.