# A Young Woman with Paraneoplastic Cushing’s Syndrome Due to a Pulmonary Carcinoid

## TL;DR

A 34-year-old woman with severe Cushing’s syndrome was diagnosed with a rare lung tumor causing excessive ACTH production.

## Contribution

The case highlights the importance of considering ectopic ACTH secretion in severe Cushing’s syndrome and the value of coordinated expert care.

## Key findings

- A persistent lung nodule was identified as a well-differentiated pulmonary carcinoid after multiple diagnostic steps.
- Surgical lobectomy led to biochemical remission of Cushing’s syndrome.
- Diagnostic delays were attributed to human factors despite early imaging clues.

## Abstract

Background and Clinical Significance: Ectopic ACTH secretion is a rare, potentially life-threatening cause of Cushing’s syndrome that can be overlooked when small neuroendocrine tumors evade standard imaging. Case Presentation: A 34-year-old woman presented with rapidly progressing clinical signs/symptoms of Cushing’s syndrome and demonstrated marked hypercortisolism (cortisol 2428 nmol/L; ACTH 163 ng/mL; urinary free cortisol 815 μg/24 h; K+ 2.4 mmol/L). Small hypermetabolic nodules were noted in her right lung on 18F-FDG PET/CT but were initially deemed to be infectious; DOTANOC PET-CT and inferior petrosal sinus sampling were non-diagnostic. After medically induced inhibition of cortisol, repeat PET/CT showed a persistent 13 mm lung nodule. Biopsy confirmed a well-differentiated pulmonary carcinoid (Ki-67 3%), and lobectomy achieved biochemical remission. Conclusions: Diagnostic delay stemmed from human factors despite early suggestive imaging. Ectopic ACTH secretion should remain high on the differential diagnosis in rapidly evolving, severe ACTH-dependent Cushing’s disease; early, decisive diagnosis and coordinated care overseen by endocrinologists—preferably in expert centers—can shorten exposure to deleteriously high cortisol levels and improve outcomes.