Atypical Pleomorphic Adenoma of the Salivary Gland: Pathological Features and HER2/neu Immunoreactivity

Abstract

1as a premalignant condition of PA. According to their report, atypical PA exhibits at least one of following pathological ndings : hypercellularity, capsule violation, hyalinization, necrosis or cellular anaplasia. However, the immunoreactivity of atypical PA for HER2 / neu, an important immunohistochemical tool for the differential diagnosis of benign PA versus carcinoma Ca ex PA 2, 3 , is still unclear. This study investigated the pathology and HER2 / neu immunoreactivity of atypical PA, compared with Ca ex PA and benign PA. Abstract : Atypical pleomorphic adenoma PA is a premalignant condition of PA, although its immunoreactivity for HER2 / neu, which is a marker for carcinoma Ca ex PA, is still unclear. We investigated the pathology and HER2 / neu immunoreactivity of atypical PA, and compared the results with Ca ex PA and benign PA cases. The mean age of atypical PA was statistically lower and the size tended to be smaller than Ca ex PA. Pathologically, hypercellularity was observed in 10 cases of atypical PA, and 8 cases showed capsule violation. Immunohistochemically, the HER2 / neu positive ratio in hypercellular foci of atypical PA was 40 , signi cantly higher than the ratio in benign PA, and significantly lower than that in Ca ex PA. However, the ratio in capsule violation foci of atypical PA was 0 , as in benign PA. Thus, hypercellularity was considered to indicate greater potential for malignant transformation than capsular violation. Further studies are needed to determine whether atypical PA with HER2 / neu expression undergoes malignant transformation more frequently than HER2 / neu-negative atypical PA.

Immunohistochemical Features of an Atypical Pleomorphic Adenoma of the Salivary Gland-Overexpression of Ki-67 and p53

“…Since then, it has been controversial whether the presence of atypical features in PA is indicative of a precancerous condition and how carcinoma arises in PA. We recently identi ed, using immunohistochemical staining, that HER2 / neu appears in 40 of h-APA. HER2 / neu is an important marker for Ca-ex-PA 2, 3 and we concluded that h-APA indicates a greater potential for malignant transformation 4 . Although there have been many reports of the high incidence of Ki-67 and p53 overexpression that correlates with malignant transformation in Ca-ex-PA cells, there have been no reports focusing on Ki-67 and p53 expression in h-APA cells [2][3][4][5][6][7][8][9][10][11] .…”

“…Since 40 of h-APA cases are positive for HER2 / neu expression 4 , we propose that p53 overexpression is a later event than HER2 / neu overexpression in the malignant transformation of APA. Further study is required to con rm the roles of p53 and HER2 / neu overexpression in this transformation.…”