Diagnostic Pitfalls in Fine Needle Aspiration of Pleomorphic Adenoma: Degenerative Changes in Myoepithelial Cells as Malignant and PLAG1 False Negativity.

Fine needle aspiration (FNA) is widely accepted as an efficient first-line diagnostic tool for evaluating salivary gland lesions. It can accurately diagnose a majority of common benign tumors, including pleomorphic adenoma (PA). However, PA can exhibit a wide range of morphological variations, which may lead to misinterpretation. Here, we present a case in which degenerative myoepithelial cells with nuclear atypia in PA were misinterpreted as malignant. Furthermore, PLAG1 false negativity in cell block material compounded the diagnostic challenge. This report aims to highlight this diagnostic pitfall and alert cytopathologists by providing an illustrative example.