Primary Endometrium Primitive Neuroectodermal Tumor with Diagnostic and Treatment Challenges: A Case Report.

Background: Primitive neuroectodermal tumor (PNET) is a rare and aggressive malignancy, with primary occurrence in the endometrium being uncommon. Due to nonspecific clinical and imaging features, it is frequently misdiagnosed, leading to delayed treatment and poor prognosis. Case Presentation: We present the case of a 26-year-old woman with persistent abnormal uterine bleeding, initially misdiagnosed as benign endometrial polyp following curettage. Subsequent imaging revealed a large intrauterine mass, and definitive diagnosis of primary endometrium PNET was established through histopathological and immunohistochemical analyses, including characteristic CD99 positivity and Homer-Wright rosettes. The patient underwent modified radical hysterectomy with lymph node dissection, followed by adjuvant chemotherapy, which was discontinued due to severe toxicity. Conclusion: This report provides further elucidation on the diagnostic challenges inherent to primary endometrium PNET, underscoring the contribution of immunohistochemical analysis in resolving differential diagnoses among small round cell tumors. Rare neoplasms should warrant consideration in young patients presenting with atypical uterine hemorrhage, particularly in scenarios where preliminary pathological findings are inconclusive. The establishment of an early and definitive diagnosis, coupled with the implementation of a multimodal treatment strategy, is fundamental to optimizing clinical outcomes for this aggressive condition.