Successful Conversion Surgery for Locally Advanced Pancreatic Neuroendocrine Carcinoma: A Case Report.

Introduction: Pancreatic neuroendocrine carcinoma (panNEC) is a poorly differentiated, highly malignant neoplasm with an extremely poor prognosis. This tumor often presents as locally advanced or unresectable at the initial diagnosis.

Case presentation: A 72-year-old woman presented to our hospital with weight loss. A computed tomography scan showed an enhanced tumor measuring 32 mm in the pancreatic head region, with contact to the common hepatic artery over 180°. The pathological findings from the specimens obtained via endoscopic ultrasonography-guided fine-needle aspiration identified small cell-type NEC with extensive necrosis, leading to a diagnosis of locally advanced unresectable panNEC. Accordingly, she began a course of carboplatin and etoposide therapy. After 7 courses, given the significant shrinkage of the tumor, we performed a pancreatoduodenectomy as a conversion surgery. Pathological examination revealed a localized, residual nodule of NEC, consisting mainly of large neoplastic cells, with carcinoma in situ components scattered within and around the nodule. In addition, the diffuse membrane expression of somatostatin receptor 2 was observed in NEC components. Each component showed the same type of KRAS mutation (p.G12V) and was considered to originate from a single primary tumor in the pancreas. She received 3 courses of the same regimen as adjuvant chemotherapy and has remained recurrence-free for 24 months.

Conclusion: This is a rare case of successful conversion surgery for locally advanced, unresectable panNEC after chemotherapy, providing several important histopathological and molecular insights.