Steroidogenic Acute Regulatory Protein (STAR) controls the rate-limiting step of steroidegenesis by translocating cholesterol from the outer mitochondrial membrane to the inner membrane where it is later cleaved to pregnenolone.It is primarily present in steroid-producing cells, including Leydig cells in the testis, theca cells and luteal cells in the ovary and adrenal cells in the adrenal cortex. Due to low levels of pregnenolone, seminomas and Leydig cell tumors display no specific STAR staining. Therefore, STAR antibody may assist in differentiating sex cord stromal tumors (SCST), seminomas and embryonal carcinomas.