Case: AP145
Contributor's Comment: This is a typical case presenting as a small round cell tumor with some degree of cohesion, and dot immunoreactivity for cytokeratin AE1/E3 and CK 20, also intense immunoreactivity for chromogranin, synaptophysin, and NSE. Pertinent negative immunostains include CK7, TTF-1, LCA, HMB45. We did not examine EM in this case, but ultrastructures would be characterized by the presence of membrane bound dense neurosecretory granules and paranuclear aggregates of cytokeratin filaments. There has been recent observation of c-KIT (CD117) expression in Merkel cell carcinoma, but we did not tested this case.