Long-Term Survival Achieved with Multimodal Therapy and Multiple Hepatic Resections for Pancreatic Primary Mixed Neuroendocrine-Non-Neuroendocrine Neoplasm Comprising Acinar Cell Carcinoma and Neuroendocrine Carcinoma: A Case Report.

INTRODUCTION: In the 2019 World Health Organization (WHO) classification, tumors comprising ≥30% of both neuroendocrine and non-neuroendocrine components are defined as mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs). Acinar cell carcinoma (ACC) constitutes <1% of pancreatic tumors, while neuroendocrine carcinoma (NEC) accounts for 1%-2%, making MiNENs with both characteristics extremely rare. The role of surgical resection in resectable NEC remains unclear; however, it is generally recommended as part of multimodal therapy. This case presents a pancreatic mixed acinar-NEC successfully managed with multimodal therapy, including repeated liver metastasis resections, achieving long-term disease control. CASE PRESENTATION: A 57-year-old woman presented with abdominal pain. Her symptoms improved with conservative treatment, but the patient returned to the emergency room 3 months later with abdominal pain. Hemorrhage from a pancreatic tail cyst and localized pancreatitis were suspected based on laboratory and imaging findings. As malignancy could not be ruled out, the patient was referred to our department and underwent laparoscopic distal pancreatectomy with splenectomy. Pathological examination revealed mixed acinar-NEC composed of 70% ACC and 30% NEC; later, liver metastasis was detected. While progression was observed after cisplatin plus etoposide combination therapy, stereotactic body radiation therapy led to a gradual reduction in the size of the liver tumor. Six months postoperatively, laparoscopic partial hepatectomy was performed. Despite adjuvant chemotherapy, a solitary liver tumor from ACC was detected 1 month after surgery. After FOLFIRINOX chemotherapy administration, another laparoscopic partial hepatectomy was performed. No recurrence has since been observed. CONCLUSIONS: In cases where disease control is achieved via multimodal therapy, surgical resection of metastases may be considered to provide long-term survival.