Advanced Neuroendocrine Carcinoma of the Ovary- Diagnostic Challenges and Therapeutic Insights - A Case Report and Literature Review

Abstract: Background: Advanced neuroendocrine carcinoma (NEC) of the ovary is an exceedingly rare and aggressive malignancy, often presenting diagnostic and therapeutic challenges. Its rarity necessitates a detailed exploration of clinical presentation, diagnostic workup, and therapeutic outcomes. Case Presentation: We report the case of a 67-year-old female who presented in August 2023 with abdominal pain, distension, and a history of recurrent malignant ascites. She was admitted and underwent diagnostic and therapeutic ascitic tapping, with 4 liters of fluid drained. Further evaluation included PET-CT imaging (August 23), which revealed FDG-avid bilateral adnexal masses, omental caking, peritoneal deposits, and moderate ascites. Histopathological examination of an omental biopsy done in August 2023 showed morphology and an immunoprofile suggestive of neuroendocrine carcinoma, small-cell type (Müllerian origin). Immunohistochemistry (IHC) demonstrated positivity for CK7, PAX8, synaptophysin, and chromogranin, with a high Ki-67 proliferation index (90-95%). Molecular profiling revealed the tumor to be proficient mismatch repair (pMMR) and microsatellite stable (MSS), with BRCA1/2 mutations negative (both germline and somatic). The patient was initiated on platinum-based chemotherapy (cisplatin and etoposide), completing six cycles with a significant initial therapeutic response noted in an interim PET-CT scan (February 2024). However, disease progression was observed with increased tumor burden on subsequent imaging (March 2024). She was transitioned to second-line therapy with the FOLFIRINOX regimen in March 2024, which showed a significant interim response on follow-up PET-CT scans (June 2024). The patient’s condition continues to be monitored, with ongoing chemotherapy providing further disease control. She completed six cycles in October 2024, and a PET-CT scan post-second-line chemotherapy showed further response. This case illustrates the challenges of managing advanced ovarian NEC, emphasizing the need for a multimodal therapeutic approach.