Primitive Neuroectodermal Tumor, Ovary
Esther Oliva, MD
Key Facts
Terminology
cPNET: Monodermal teratoma composed of tissues closely resembling central nervous system neoplasms with variable degrees of differentiation
pPNET: Malignant small round blue cell tumor, some with EWSR1 rearrangement
Microscopic Pathology
cPNET: Differentiated (ependymoma), primitive (medulloepithelioma, neuroblastoma, ependymoblastoma, medulloblastoma), anaplastic (glioblastoma multiforme)
Teratoma, endometrioid carcinoma, adenosarcoma, or malignant mixed mesodermal tumor may be seen
Ancillary Tests
FLI-1 & CD99 (+), CD56(+/-); GFAP(+) if cPNET
EWSR1 gene rearrangement if pPNET
Top Differential Diagnoses
Immature teratoma
 Differentiated central-type neuroectodermal tumors mimic the appearance of ependymoma, showing cells with fibrillary processes and perivascular rosettes. |
 If a primitive neuroectodermal tumor (PNET) is composed of primitive cells growing in sheets without evident central nervous system differentiation, peripheraltype PNET (pPNET) tumor should be excluded. |
TERMINOLOGY
Abbreviations
Primitive neuroectodermal tumor (PNET)
Central-type primitive neuroectodermal tumor (cPNET)
Peripheral-type primitive neuroectodermal tumor (pPNET)
Definitions
cPNET: Malignant monodermal teratoma composed of tissues closely resembling central nervous system neoplasms with variable degrees of differentiation
pPNET: Malignant small round blue cell tumor, some with EWSR1 rearrangement
ETIOLOGY/PATHOGENESIS
Malignant Transformation (cPNET)
From preexistent central nervous tissue within teratoma
CLINICAL ISSUES
