Pleomorphic adenoma (PA) is the most common salivary gland neoplasm, and its diagnosis is straightforward in the majority of cases. However, not infrequently, PA shows unusual and uncommon histological features that can be confused with those of malignancy. The difficulties in diagnosing PA arise from its ability to mimic invasion, show atypical or metaplastic cytomorphology, and show morphological features that overlap with those of established salivary gland carcinomas. In addition, recognising early malignant transformation to carcinoma ex-pleomorphic adenoma continues to be a frequent challenge. This review describes the diagnostic pitfalls of PA, and offers a systematic approach to avoid them by combining classic histopathology with novel immunohistochemical and molecular tests.

Department of Oncology Section Head and Neck Oncology KU Leuven Leuven Belgium

Department of Otolaryngology University of Udine Udine Italy

Department of Otorhinolaryngology and Head and Neck Surgery University Hospital Bern Switzerland

Department of Pathology Faculty of Medicine in Plzen Charles University Plzen Czech Republic

Department of Pathology Moffitt Cancer Center Tampa FL USA

Department of Translational Research and of New Technologies in Medicine and Surgery University of Pisa Pisa Italy

International Head and Neck Scientific Group Padua Italy

Otorhinolaryngology Head and Neck Surgery Leuven Cancer Institute University Hospitals Leuven Leuven Belgium

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