KRT7 and neoplasm: Immunohistochemically, the tumor cells are positive for cytokeratin 7 (CK7), epithelial membrane antigen (EMA), gross cystic disease fluid protein 15 (GCDFP-15), GATA binding protein 3 (GATA3), synaptophysin, chromogranin, neural cell adhesion molecule (CD56), and neuron-specific enolase (NSE), suggesting biphasic differentiation toward both apocrine sweat glands and neuroendocrine cells (5).