The Melanoma-associated antigen C2, MAGEC2, also known as CT10, was identified as a novel Cancer/testis (CT)-antigen originally identified in the SK-MEL-37 melanoma cell line.  MAGEC2 is a member of the MAGEC gene family, mapping to chromosome Xq26-q27 and is closely related to MAGEC1 (CT7).  CT-X antigens are thought to repress the expression of certain genes necessary for cellular differentiation.  MAGEC2 expression is restricted to the testis in normal tissues.  Male germ cells highly express MAGEC2 during early phases of spermatogenesis.  Immature spermatogonia and spermatocyte demonstrated strong MAGEC2 nuclear expression and is decreased in spermatids.  MAGEC2 is not expressed in mature sperm and surrounding stromal, Sertoli, and Leydig cells.    Bode, et al. examined 325 testicular germ cell tumors and found MAGEC2 in most seminoma (94%), spermatocytic seminoma (100%) and intratubular germ cell neoplasia (IGCNU) (100%).  Conversely, MAGEC2 expression were uncommon in embryonal carcinoma, yolk sac tumor, teratoma and choriocarcinoma.    MAGEC2 protein expression is a sensitive marker for seminomas, spermatocytic seminomas, and IGCNU.  Use of this marker may be helpful in the diagnosing seminoma (positive) from embryonal carcinoma (negative) when assessed in a panel of germ cell tumor markers including OCT4, KIT, PLAP, CD30, SOX2 and SOX17.  Additionally, MAGEC2 was identified as a prognostic marker in a variety of tumor types.  MAGEC2 positive tumors were frequently associated with reduced recurrence free and overall survival rates in prostate, hepatocellular, triple-negative breast, and non-small cell lung carcinomas.