Ampullary Neuroendocrine Carcinoma Presenting with Clinically Confirmed Endogenous Hyperinsulinemic Hypoglycemia
Abstract
A 65-year-old man without diabetes presented with fasting hypoglycemia. During a fasting test, plasma glucose decreased to 46 mg/dL with inappropriately elevated insulin (11.1 μU/mL) and C-peptide (8.7 ng/mL) levels, confirming endogenous hyperinsulinemic hypoglycemia. Imaging revealed a tumor of the ampulla of Vater with multiple liver metastases but no pancreatic lesions. An endoscopic biopsy revealed poorly differentiated small cell-type NEC with a Ki-67 index >90% and complete loss of RB1 expression. Despite negative insulin immunostaining, dynamic endocrine testing confirmed endogenous hyperinsulinemic hypoglycemia. These findings were clinically consistent with ectopic insulin secretion from the NEC, although pathological confirmation was not obtained in this case. This case highlights the importance of integrating physiological, radiological, and pathological findings when evaluating suspected ectopic insulin secretion.
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BibTeX
@article{ito2026ampullary,
title = {{Ampullary Neuroendocrine Carcinoma Presenting with Clinically Confirmed Endogenous Hyperinsulinemic Hypoglycemia}},
author = {Mika Ito and Eiki Ishisaka and Yoshiro Kashii and Yuno Goto and Yukimatsu Yoshio and Waka Sakai and Tomoki Kameyama and Masakiyo Sasahara and Tomoko Norose and Nobuyuki Ohike},
journal = {Internal Medicine},
year = {2026},
month = oct,
doi = {10.2169/internalmedicine.7605-26},
url = {https://www.jstage.jst.go.jp/article/internalmedicine/advpub/0/advpub_7605-26/_article},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Ampullary Neuroendocrine Carcinoma Presenting with Clinically Confirmed Endogenous Hyperinsulinemic Hypoglycemia
AU - Mika Ito
AU - Eiki Ishisaka
AU - Yoshiro Kashii
AU - Yuno Goto
AU - Yukimatsu Yoshio
AU - Waka Sakai
AU - Tomoki Kameyama
AU - Masakiyo Sasahara
AU - Tomoko Norose
AU - Nobuyuki Ohike
PY - 2026
DA - 2026/10/15
JO - Internal Medicine
DO - 10.2169/internalmedicine.7605-26
UR - https://www.jstage.jst.go.jp/article/internalmedicine/advpub/0/advpub_7605-26/_article
AB - A 65-year-old man without diabetes presented with fasting hypoglycemia. During a fasting test, plasma glucose decreased to 46 mg/dL with inappropriately elevated insulin (11.1 μU/mL) and C-peptide (8.7 ng/mL) levels, confirming endogenous hyperinsulinemic hypoglycemia. Imaging revealed a tumor of the ampulla of Vater with multiple liver metastases but no pancreatic lesions. An endoscopic biopsy revealed poorly differentiated small cell-type NEC with a Ki-67 index >90% and complete loss of RB1 expression. Despite negative insulin immunostaining, dynamic endocrine testing confirmed endogenous hyperinsulinemic hypoglycemia. These findings were clinically consistent with ectopic insulin secretion from the NEC, although pathological confirmation was not obtained in this case. This case highlights the importance of integrating physiological, radiological, and pathological findings when evaluating suspected ectopic insulin secretion.
SN - 1349-7235
SN - 0918-2918
ER -