Abstract
Oncocytic adrenal cortical carcinoma (ACC) is a rare malignant adrenal cortical tumor with limited documented case reports. Herein, a 65-year-old female patient presented with a large, solid adrenal mass. A diagnosis of oncocytic ACC was rendered with the following tumor characteristics: The tumor entirely consists of diffuse sheets of polygonal cells with bizarre nuclear atypia and deeply eosinophilic cytoplasm. The panel of immunohistochemistry revealed its adrenocortical nature, with synaptophysin and melan-A expression and the corresponding negativity of pancytokeratin and chromogranin. Moreover, an ultrastructural demonstration of the oncocytic nature of the mass is also presented.