ABSTRACT
Grossly, the tumor is highly vascular and may contain intratumoral hemorrhage. Microscopically, the tumor appears as a small round cell tumor, such as a poorly differentiated carcinoma, melanoma or other neuroectodermal tumor. Immunohistochemical stains are helpful because all of the neuroendocrine markers are positive. These include neuron-specific enolase, chromogranins, synaptophysin and the neuronal marker anti-Hu. Epithelial markers such as cytokeratin and epithelial membrane antigen (EMA) are absent. The MIB-1 index can be as high as 50%.
