Amplification of MDM2 and Loss of p16 Expression: Do They Have a Role in Malignant Transformation of Ovarian Brenner Tumor?

Objectives To review the significance of MDM2 and cyclin D1 expression and loss of p16 expression in malignant and borderline Brenner tumors (BTs) of the ovary. Methods We describe 2 new cases of ovarian BT, 1 malignant and 1 borderline. We studied MDM2, p16, and cyclin D1 expression by immunohistochemistry in the benign, borderline, and malignant components of these 2 cases and in 5 additional cases of benign BT. We also reviewed and summarized the literature on the clinical, immunohistochemical and molecular characteristics of borderline and malignant BTs (BdBTs and MBTs). Results Nuclear expression of MDM2 was seen only in the MBT. Loss of p16 expression was seen in both BdBT and MBT. Cyclin D1 expression was in proportion to the degree of malignancy. Amplification of MDM2, loss of CDKN2A (p16-encoding gene), and amplification of CCND1 (cyclin D1–encoding gene) were confirmed by commercial next-generation sequencing in the case of MBT. Conclusions We are the first to report immunohistochemical expression of MDM2 in an MBT. Amplification of MDM2 and loss of p16 expression may have a role in malignant transformation of BT.