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Pleomorphic adenoma(PA)is the most common benign tumor in salivary glands. There are many reports of clinical and histopathological studies of PA, although the majority of these are studies of PA of the parotid gland. Although PA is a benign tumor, there is a risk of recurrence or malignant transformation, which can make clinical treatment difficult. Clarifying the differences in tumor characteristics depending on the site of occurrence may aid clinical management. In this study, to understand the detail histopathological characteristics of this tumor having various histological features, the previous cases of minor salivary gland, parotid gland, and submandibular gland were subclassified according to Seifert's classification, and then occurrent attitude of the parenchyma and stromal component were analyzed. This retrospective study included 104 cases that had been diagnosed with PA and treated from 1985 to 2019. The cases were clinically and histopathologically analyzed by two oral pathologists for a definite diagnosis. The PAs were classified according to the classification described by Seifert et al. Our analysis showed 31.7% of the cases were subtype 1, 17.3% were subtype 2a, 1% were subtype 2b, 11.5% were subtype 2c, 25% were subtype 2e, 10.6% were subtype 3, and 2.9% were subtype 4. No cases of subtype 2d were found. Significant differences in the frequencies of occurrence of subtypes were found between the major and minor salivary glands. Differences were observed in the stromal components and their composition(subtypes)between the major and minor salivary glands. The histological differences between PAs from minor and major salivary glands may be partially explained by the anatomical differences between these two sites.
Yamamoto et al. (Fri,) studied this question.