Mixed Epithelial & Stromal Tumor : Myosin

Mixed epithelial and stromal tumor (MEST): The immunohistochemical profile of MEST is as follows. POSITIVE MARKERS: The stromal component expresses estrogen receptors and progesterone receptors in >90% of cases indicating the role of steroid hormones in its pathogenesis. Other frequently positive markers include smooth muscle actin, desmin, myosin (shown here), caldesmon and CD10. Epithelial elements are consistently positive for keratins and PAX8. CD34, GATA3 and WT1 are positive in 50% of cases or less. NEGATIVE MARKERS: Consistently negative markers include inhibin, SF1, HMB45, Melan A, and cathepsin K.