<![CDATA[Introduction: Polymorphous adenocarcinoma (PAC) is a rare, low-grade malignancy primarily arising in the minor salivary glands, accounting for 1-6% of head and neck tumors. It commonly affects the palate, but can rarely manifest in major salivary glands, such as the parotid gland. Although typically indolent, PAC can undergo high-grade transformation (HGT), which presents with histologically aggressive features such as nuclear atypia, high mitotic activity, and extensive necrosis. Distinguishing PAC with HGT from other salivary gland carcinomas is clinically challenging due to its architectural diversity, absence of pathognomonic signs, and overlapping features with other malignancies. Accurate diagnosis is essential, as prognosis and treatment options may vary. This report aims to highlight the diagnostic challenge, raise awareness, and encourage consideration of this disease in the differential diagnosis of salivary gland lesions.Case Presentation: This report presents a rare case of high-grade PAC from the parotid gland, mimicking salivary duct carcinoma (SDC). A 79-year-old male presented with a painless mass on the right cheek, growing over six months. Examination revealed a firm, immobile mass, and biopsy indicated solid growth with extensive necrosis and significant polymorphism. Immunohistochemistry for androgen receptors (AR) and p63 confirmed PAC, distinguishing it from other malignancies like SDC and mucoepidermoid carcinoma. The patient underwent chemotherapy, however, follow-up histopathological examination showed residual PAC with persistent polymorphism and mitotic activity.Conclusions: Polymorphous adenocarcinoma is a rare, low-grade malignancy of the salivary gland that is often underdiagnosed and underreported. Instances of high-grade transformation has made the diagnosis of this entity difficult due to similarities to other malignancies. This case highlights the diagnostic challenges of PAC, especially with HGT, and underscores the importance of immunohistochemistry for accurate diagnosis and treatment planning. Early recognition and differentiation from other salivary gland malignancies are crucial for appropriate management.]]>
