CD99 Immunoreactivity in Metastatic Malignant Melanoma

Abstract

CD99, also known as p30/32, is a glycoprotein product of the MIC2 gene, which is located on the short arm of both chromosome X and Y. This transmembrane protein was originally utilized in immunohistochemistry as a unique marker for Ewing sarcoma, other primitive neuroectodermal tumors, and more recently in a wide variety of tumors. It’s expression in malignant melanoma (MM) has not been well documented. A recent study at our institution demonstrated membranous staining in approximately 61% of primary MM. As CD99 is expressed by hematopoeitic cells, it has been proposed as a mechanism for lymphocytes to gain access to the vasculature.1 This study is designed to determine if CD99 expression in melanoma cells has a similar role using cases of metastatic MM from our archives. Our evaluation shows that 13 of 28 cases (46.4%) demonstrated membranous CD99 staining. A case of this magnitude has not been previously reported. Reference: 1. Shenkel AR, Mamdouh Z, Chen X, Liebman RM, Muller WA. CD99 plays a major role in the migration of monocytes through endothelial junctions. Nature Immunol 2002;3:143–150.