PRIMITIVE NEUROECTODERMAL TUMOR ARISING IN AN OVARIAN MATURE CYSTIC TERATOMA - IMMUNOHISTOCHEMICAL AND ELECTRON-MICROSCOPIC STUDIES

The occurrence of a malignant neuroectodermal tumor in a mature cystic teratoma is extremely rare. Five cases of ovarian primitive neuroecto dermal tumors (PNET) or neuroepitheliomas have been reported. In two, the tumor was adjacent to foci of a mature teratomatous element. We pr esent the immunohistochemical profile and electron microscopic study o f an ovarian mature cystic teratoma with PNET or malignant neuroepithe lioma. The transition between the mature neural elements and the malig nant PNET presents a model for monodermic neuroepithelial differentiat ion and explains the histogenesis of this unusual tumor.