Polymorphous low‐grade adenocarcinoma of the salivary glands with transformation to high‐grade carcinoma

Abstract

Polymorphous low-grade adenocarcinoma was first described relatively recently, and as experience with it continues to accumulate, it is becoming clear that late recurrences and metastases, whilst still infrequent, may not be quite as rare as previously thought. Reports of histological transformation are even scarcer, and most occurred at least 13 years after the polymorphous low-grade adenocarcinoma was initially recognized. It is a real possibility that this phenomenon, like clinical progression, may also be encountered more often as time passes. Therefore, we believe that, whilst polymorphous low-grade adenocarcinoma is certainly far less aggressive than, for example, adenoid cystic carcinoma, it nevertheless remains a true malignancy with a potential to prove fatal in a minority of patients.