A Rare Case of Metastatic Adrenocorticotrophic Hormone –Secreting Pancreatic Neuroendocrine Tumor Causing Ectopic Cushing Syndrome in a 46-Year-Old Woman

BACKGROUND Adrenocorticotrophic hormone (ACTH)-secreting pancreatic neuroendocrine tumors (pNETs) are rare and poorly understood entities. Only 1-2% of pancreatic neoplasms are pNETs, and even fewer are hormone-secreting. They can present indolently or with overt Cushing syndrome. Their diagnosis involves complex multi-modal imaging and laboratory evaluation. Management includes medications, such as somatostatin analogs and ketoconazole, as well as surgical resection for definitive treatment. This report describes a 46-year-old woman who presented with overt Cushing syndrome and was ultimately diagnosed with a pNET. CASE REPORT This patient's initial symptoms and laboratory testing were consistent with Cushing syndrome. A high-dose dexamethasone suppression test suggested ectopic ACTH production, and magnetic resonance imaging (MRI) of the brain showed a pituitary microadenoma. However, computed tomography (CT) of the abdomen and endoscopic ultrasound-guided biopsy with immunohistochemistry confirmed a pancreatic mass as the source of ACTH production with potential hepatic metastasis. Her Cushing syndrome was managed with ketoconazole and octreotide. Subsequently, >99% of the pNET was surgically removed, resulting in reversal of her Cushing syndrome. Currently, she is being monitored closely for recurrence. CONCLUSIONS Our management of this ACTH-secreting pNET highlights the complexities of diagnosis and multidisciplinary treatment options, which are underrepresented in the current literature on this rare entity. This case emphasizes the challenges in evaluation, including the importance of early and precise diagnosis in the face of potential confounders.