Immunohistochemical identification of salivary pleomorphic adenoma subtypes using p63 and alpha smooth muscle actin myoepithelial markers

Abstract

Adeola M. Ladeji, Kehinde E. Adebiyi, Akinwumi Komolafe, Olujide O. Soyele, Mofoluwaso Olajide,Henry A. Adeola,

Background: Pleomorphic adenoma (PA) histopathologically represents a heterogeneous lesion with varying proportion of mesenchymal and epithelial tissue. Due to its heterogeneity, identifying various subtypes often presents a diagnostic dilemma. Hence, the aim of this study is to determine and compare the activities of salivary myoepithelial (myo) and basal reserve cells (BRC) within the subtypes of salivary PA using p63 and alpha smooth muscle actin (α-SMA) immunohistochemical markers. Method: In this retrospective study, 24 archival tissue blocks of PA (12 stroma-rich, 6 cell-rich, and 6 classic subtypes) retrieved and subjected to immunohistochemistry using monoclonal p63 and α-SMA antibodies. Fraction of positive cells expressed as the percentage of total cells within each sample, labeling indices (LI) was computed. Result: PA samples subjected to immunohistochemistry showed 100% p63 and 95.9% α-SMA immunoreactivity. Statistically significant difference (p = 0.01) was observed with p63 mean LI across PA subtypes. Overall, p63 LI (37.1 ± 13.5) was higher than α-SMA LI (26.5 ± 9.5). Staining pattern for both markers was similar within epithelial and stroma elements. Conclusion: Disparity in Mean LI of the markers with higher index observed for p63, suggests additional activity of BRC, whose variable expression is associated with the differential ratio of epithelial to stroma components within PA subtypes.