# Ectopic Cushing Syndrome Due to a Large Mediastinal Neuroendocrine Tumor

## TL;DR

A 33-year-old man with severe Cushing syndrome caused by a rare mediastinal tumor required complex multidisciplinary treatment due to the tumor's aggressive nature and location.

## Contribution

This case highlights the challenges in managing ectopic Cushing syndrome from a high-grade mediastinal neuroendocrine tumor.

## Key findings

- The patient had high ACTH and cortisol levels due to a mediastinal tumor producing ACTH.
- Debulking surgery was performed before adrenalectomy due to high surgical risk from tumor location.
- The tumor was more aggressive than initially expected and had metastasized.

## Abstract

Ectopic Cushing syndrome is an uncommon cause of hypercortisolism that needs rapid recognition and treatment to reduce complications. Here, we present the case of a 33-year-old man with a 1-year history of severe Cushing syndrome. Biochemical findings showed both high ACTH and 24-hour urine free cortisol, and nonsuppressed morning serum cortisol. The 18fluorine-1,4,7-triazacyclononane-1,4,7-triacetate-octreotide positron emission tomography/computed tomography revealed a large mediastinal tumor with high uptake. Initial biopsy reported a grade 1 neuroendocrine tumor with positive ACTH immunostaining. Treatment was initiated with ketoconazole and somatostatin analog. To achieve rapid Cushing syndrome control, etomidate intravenous infusion was started. After multidisciplinary assessment and because of high surgical risk (concern for airway compromise from tumor location above the trachea, size, and possible mechanical lung compression with laparoscopic adrenalectomy) debulking surgery of the primary tumor was performed first, followed by bilateral adrenalectomy. Pathology findings of the R2 tumor showed a higher grade tumor than previously reported and an 18 Fluorodeoxyglucose positron emission tomography/computed tomography demonstrated distant metastatic disease. In summary, severe hypercortisolism usually occurs in the setting of ectopic production, it can be debilitating with increased mortality, and in this case, tumor aggressiveness and location made management particularly challenging, requiring a multidisciplinary approach.