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HMGA 2 is a specific immunohistochemical marker for pleomorphic adenoma and carcinoma ex‐pleomorphic adenoma
Author(s) -
Mito Jeffrey K,
Jo Vickie Y,
Chiosea Simion I,
Dal Cin Paola,
Krane Jeffrey F
Publication year - 2017
Publication title -
histopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.626
H-Index - 124
eISSN - 1365-2559
pISSN - 0309-0167
DOI - 10.1111/his.13246
Subject(s) - carcinoma ex pleomorphic adenoma , pathology , biology , pleomorphic adenoma , myoepithelial cell , salivary gland , immunohistochemistry , adenoma , medicine
Aims Accurate classification of salivary gland neoplasms may be challenging, owing to morphological overlap, particularly in small biopsies. Recurrent translocations involving the high‐mobility group AT ‐hook 2 ( HMGA 2) gene are present in a subset of pleomorphic adenomas ( PA s) and carcinoma ex‐pleomorphic adenomas ( CA ex‐ PA s). The aim of this study was to evaluate immunohistochemical HMGA 2 expression in 225 salivary gland tumours, including 56 PA s, 37 CA ex‐ PA s, and 132 potential histological mimics, to determine its diagnostic utility. Methods and results HMGA 2 expression was identified in 19 PA s (33.9%) and nine CA ex‐ PA s (24.3%). Expression was strong and diffuse throughout all PA s, and in four of nine positive CA ex‐ PA s. In five CA ex‐ PA s, HMGA 2 showed weak‐to‐strong multifocal staining within the carcinomatous component, and strong diffuse HMGA 2 expression in the residual PA . Among histological mimics, six de‐novo salivary duct carcinomas (28.5%), three epithelial–myoepithelial carcinomas (33.3%) and one case each of myoepithelioma and basal cell adenoma expressed HMGA 2. Fluorescence in‐situ hybridization for HMGA 2 rearrangement performed on a subset of tumours that showed diffuse HMGA 2 expression in PA s and CA ex‐ PA s was frequently associated with rearrangement of the HMGA 2 locus, whereas cases of de‐novo salivary duct carcinoma, or CA ex‐ PA with limited or no HMGA 2 expression, had an intact HMGA 2 locus. Conclusions HMGA 2 expression is a highly specific (96.2%), but low‐sensitivity (29.8%), marker for PA and CA ex‐ PA when compared with histological mimics, and is frequently associated with rearrangement of the HMGA 2 locus.