Ultrasound and Histopathologic Correlation of Ovarian Cystadenofibromas: Diagnostic Value of the "Shadow Sign"

Cystadenofibromas (CAFs) are rare benign ovarian tumors without a widely accepted ultrasound (US) pattern. They are usually described by as thin-walled, unilocular or multilocular, and at times septated cysts with scant blood flow and no solid components. We describe a unique US feature, the "shadow sign," seen in prospectively diagnosed benign CAFs. We also provide the histopathologic basis for this typical US appearance.

Ultrasound (US) examinations were performed in our obstetric and gynecologic US unit. Pathologic examinations were performed by a dedicated gynecologic pathology team. The US and pathology department's database was searched for the diagnosis of a CAF between 2010 and 2017.

We identified 20 patients who underwent transvaginal US examinations with a sole US diagnosis of a CAF, and the tumors were surgically removed. The common US feature across the 20 cases was the presence of hyperechoic avascular shadowing nodules. The correlating histologic features were unilocular or multilocular cysts with a smooth internal wall surface lined by a simple epithelium and occasional robust polypoid fibrous stroma.

This US marker helps in differentiating CAFs from borderline ovarian tumors, which do not show this US feature. We hope that recognizing the suggested shadow sign as an additional descriptor of CAFs will lead to minimizing their unnecessary removal and eliminating additional and unnecessary imaging by computed tomography and magnetic resonance imaging.