# Ectopic Adrenocorticotropic Hormone Syndrome Secondary to Pulmonary Neuroendocrine Tumor: Medical Stabilization Enables Serial Imaging and Localization

## TL;DR

A patient with a rare hormone disorder had a hidden tumor successfully found and removed through medical treatment and repeated imaging.

## Contribution

Medical stabilization allows for serial imaging to locate occult tumors causing ectopic ACTH syndrome.

## Key findings

- Medical therapy enabled biochemical control and allowed for tumor localization via serial imaging.
- An 8 mm pulmonary carcinoid was identified and surgically removed after being undetectable on functional imaging.
- Curative resection was achieved without the need for bilateral adrenalectomy.

## Abstract

Ectopic adrenocorticotropic hormone (ACTH) syndrome accounts for 15% to 20% of Cushing syndrome cases with unique diagnostic challenges. Tumor localization remains difficult, with approximately 20% of cases having occult sources despite extensive imaging. This report describes a patient whose initially occult tumor was successfully localized through serial imaging enabled by medical stabilization, resulting in curative surgical resection.

Thirty-nine-year-old woman presented with progressive weight gain, new-onset hypertension, hypokalemia, proximal muscle weakness, and cushingoid features. Laboratory evaluation demonstrated severe hypercortisolism with markedly elevated ACTH levels, and inferior petrosal sinus sampling confirmed the diagnosis of ectopic ACTH syndrome. Despite comprehensive imaging—including cross-sectional studies, gallium-68 (68Ga)-DOTA-D-Phe1,Tyr3-octreotate positron emission tomography/computed tomography, and FDG PET/CT—the ectopic source remained elusive. Medical therapy with ketoconazole and metyrapone achieved rapid biochemical control. An 8 mm lingular pulmonary nodule, non-avid on both DOTATATE and FDG PET but identified on the CT portion of FDG PET/CT, was surgically resected, resulting in complete biochemical cure.

This case highlights medical stabilization's critical role when tumor localization is initially unsuccessful, enabling serial anatomic imaging that identified an 8 mm pulmonary carcinoid initially obscured by atelectasis and nonavid on functional imaging. Small, well-differentiated neuroendocrine tumors can cause severe hypercortisolism, yet remain undetectable on DOTATATE and FDG PET.

This case demonstrates that medical stabilization achieves rapid biochemical control, providing time for serial anatomic imaging to localize occult ectopic ACTH sources. A small pulmonary carcinoid initially obscured by atelectasis and non:avid on functional imaging was identified through repeat CT comparison, enabling curative resection and avoiding bilateral adrenalectomy.