Catastrophic ACTH-secreting pheochromocytoma: an uncommon and challenging entity with multifaceted presentation

Abstract

Summary: Cushing's syndrome due to ectopic adrenocorticotropic hormone (ACTH) secretion (EAS) by a pheochromocytoma is a challenging condition. A woman with hypertension and an anamnestic report of a 'non-secreting' left adrenal mass developed uncontrolled blood pressure (BP), hyperglycaemia and severe hypokalaemia. ACTH-dependent severe hypercortisolism was ascertained in the absence of Cushingoid features, and a psycho-organic syndrome developed. Brain imaging revealed a splenial lesion of the corpus callosum and a pituitary microadenoma. The adrenal mass displayed high uptake on both 18F-FDG PET/CT and 68Ga-DOTATOC PET/CT; urinary metanephrine levels were greatly increased. The combination of antihypertensive drugs, high-dose potassium infusion, insulin and steroidogenesis inhibitor normalized BP, metabolic parameters and cortisol levels; laparoscopic left adrenalectomy under intravenous hydrocortisone infusion was performed. On combined histology and immunohistochemistry, an ACTH-secreting pheochromocytoma was diagnosed. The patient's clinical condition improved and remission of both hypercortisolism and catecholamine hypersecretion ensued. Brain magnetic resonance imaging showed a reduction of the splenial lesion. Off-therapy BP and metabolic parameters remained normal. The patient was discharged on cortisone replacement therapy for post-surgical hypocortisolism. EAS due to pheochromocytoma displays multifaceted clinical features and requires prompt diagnosis and multidisciplinary management in order to overcome the related severe clinical derangements.

Learning points: A small but significant number of cases of adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome are caused by ectopic ACTH secretion by neuroendocrine tumours, which is usually associated with severe hypercortisolism causing severe clinical and metabolic derangements. Ectopic ACTH secretion by a pheochromocytoma is exceedingly rare but can be life-threatening, owing to the simultaneous excess of both cortisol and catecholamines. The combination of biochemical and hormonal testing and imaging procedures is mandatory for the diagnosis of ectopic ACTH secretion, and in the presence of an adrenal mass, the possibility of an ACTH-secreting pheochromocytoma should be taken into account. Immediate-acting steroidogenesis inhibitors are required for the treatment of hypercortisolism, and catecholamine excess should also be appropriately managed before surgical removal of the tumour. A multidisciplinary approach is required for the treatment of this challenging entity.

Figure 1

Non-enhanced CT showing a hypodense area of the splenium of the corpus callosum (arrows), without mass effect (A, axial view). Contrast-enhanced MR image showing a hypointense pituitary lesion (arrow) which enhances more slowly than normal pituitary parenchyma, deemed suspicious for microadenoma (B, coronal view). FLAIR MR image showing hyperintense signal of the splenium of the corpus callosum (asterisk), which partially extended to the crux of the left fornix (arrow) (C, axial view). As the lesion showed no restricted diffusion on DWI (D, axial view), an ischaemic lesion was excluded. A progressive reduction in the extension of the hyperintense signal in the splenium of the corpus callosum (arrowheads) and in the crux of the left fornix (arrows) was observed on FLAIR MR images (2 months (E); 3 months (F); axial view). CT, computed tomography; DWI, diffusion-weighted imaging; FLAIR, fluid-attenuated inversion recovery; MR, magnetic resonance.

Figure 2

Contrast-enhanced abdominal computed tomography showing a 3-cm left adrenal mass (arrow) with well-defined margins and inhomogeneus enhancement, deemed compatible with an adenoma (A, coronal view; B, axial view). The adrenal mass showed high uptake (SUV max: 7.3) on ¹⁸F-FDG PET/CT (C, coronal view; D, axial view).

Figure 3

The left adrenal mass displaying very high uptake (SUV max: 40) on ⁶⁸Ga-DOTATOC PET/CT (arrow, axial view).

Figure 4

ACTH and cortisol levels throughout the patient’s hospitalization and follow-up.

Figure 5

Histological images of adrenal pheochromocytoma: the tumour is composed of well-defined nests of cells (‘zellballen’) (A; haematoxylin-eosin stain (HE), ×20) with pleomorphic nuclei with prominent nucleoli, basophilic or granular amphophilic cytoplasm (B; HE, ×40). The mitotic index was low: 1 mitosis per 30 high-power fields, and Ki-67 was 1%. On immunohistochemistry, cytoplasmatic ACTH staining was found in about 30% of tumour cells (C; ×20), whereas most tumour cells were stained for chromogranin A (D; ×20).