Living Donor Liver Transplantation for Vasoactive Intestinal Peptide-Secreting Tumors with Watery Diarrhea, Hypokalemia, and Achlorhydria Syndrome Resulting from Transformation of a Nonfunctional Pancreatic Neuroendocrine Tumor with Multiple Liver Metastases: A Case Report.

INTRODUCTION

Pancreatic neuroendocrine neoplasms (PNENs) are a rare subtype of neuroendocrine neoplasms (NENs), some of which cause characteristic clinical syndromes due to hormone hypersecretion. Vasoactive intestinal peptide-secreting tumors (VIPomas) produce vasoactive intestinal peptide (VIP) and are associated with watery diarrhea, hypokalemia, and achlorhydria (WDHA) syndrome, often leading to severe treatment-refractory symptoms. Although liver transplantation (LT) is regarded as a promising option for unresectable, liver-limited NENs, studies focusing on VIPoma remain limited, as do reports of transformation from nonfunctional pancreatic NENs (PNENs) to VIPoma. Furthermore, to the best of our knowledge, no cases have described progression to LT after such a transformation. Therefore, we report this case.

CASE PRESENTATION: A 65-year-old woman with nonfunctional PNEN G2 and multiple liver metastases underwent multimodal treatment including a multi-kinase inhibitor, somatostatin analogs, a mechanistic target of rapamycin (mTOR) inhibitors, and peptide receptor radionuclide therapy (PRRT). During treatment, the tumor acquired VIP-secreting capacity and transformed into a VIPoma, resulting in WDHA syndrome characterized by intractable watery diarrhea, severe electrolyte imbalance, and metabolic acidosis. Because neither conservative management nor debulking surgery achieved adequate symptom control, and no extrahepatic disease was identified, living donor LT (LDLT) was performed. After transplantation, the diarrhea resolved promptly, and no recurrence has been observed 1 year post-transplantation.

CONCLUSIONS

We report a rare case in which a nonfunctional PNEN transformed into a VIPoma during the clinical course, leading to severe WDHA syndrome. LDLT for liver-limited disease may represent an effective therapeutic option for both tumor control and symptom relief in carefully selected patients.