Primary Peripheral Primitive Neuroectodermal Tumor of the Ovary With an Epithelial Cyst : A Case Report and Review of Literature

Abstract

Peripheral primitive neuroectodermal tumor (pPNET) has some histologic resemblance to a classic central primitive neuroectodermal tumor (cPNET), however it is distinctively different from cPNET by its CD99 immunoreactivity, characteristic chromosomal translocation, t(11;22)(q24:q12) and EWS/FLI-1 chimeric mRNA. Peripheral PNETs have a predilection for soft tissues rather than for viscera. Only 15 cases of primary ovarian PNET have been reported, and only one case was proven to be pPNET. Ovarian PNET is an aggressive tumor. We report a case of a 40-year-old Thai woman with a Stage IIIb right ovarian PNET is an aggressive tumor. Despite debulking operation and vigorous adjuvant chemotherapy, the patient died of disease 6 months later. Grossly, the tumor was solid and cystic. Microscopically, the former displayed unique features mimicking cPNET, but the pPNET phenotype was validated by CD99 staining. The solid portion also contained mucin-producing gland-like structures, previously described as ependymal diffentiation. In the cystic portion, the histology demonstrated epithelial linning tissue resembling cystadenoma of borderline malignancy of the ovary. It is generally accepted that both cPNET and pPNETs can have polyphenotypic differentiation. PNETs can be originated from either totipotential germ cells, neural crest remnant or mullerian-derived cells.