A Rare Malignant Transformation in Pleomorphic Adenoma

Abstract

Carcinoma ex pleomorphic adenoma (Ca ex PA) is a rare type of malignant salivary gland tumor. Myoepithelial carcinoma (MEC) as the malignant component in Ca ex PA is an even rarer occurrence. Preoperative pathological diagnosis of Ca ex PA often goes unnoticed in many cases as they may be clinically indolent and the malignant component may not be picked up on fine-needle aspiration cytology. However, features such as rapid growth, recurrent tumor, and pain point toward a malignant transformation. We present a case of a 40-year-old female who presented with a history of recurrent swelling over parotid region with cytological diagnosis of pleomorphic adenoma, which on excision was reported as Ca ex PA with MEC being the malignant constituent. Till date, few cases of MEC arising from PA have been reported. It presents as a diagnostic challenge to both clinicians and pathologists alike; prognosis is still not clear due to few number of cases and lack of follow-up in most of them.