Adrenal Tumors and Incidentalomas

Adrenal tumours are growths arising in the adrenal cortex or medulla, ranging from common benign adenomas to rare adrenocortical carcinoma. An adrenal incidentaloma is a mass discovered unexpectedly on imaging performed for an unrelated reason. The two central questions for any adrenal mass are whether it secretes hormone (is functioning) and whether it is benign or malignant, and these questions organise the entire evaluation.

Definition

Adrenal tumours are neoplasms of adrenal cortical or medullary tissue; an adrenal incidentaloma is an adrenal mass, generally one centimetre or larger, detected incidentally on imaging done for indications unrelated to suspected adrenal disease.

Scope

This entry covers the spectrum of adrenal masses, the concept and importance of the incidentaloma, the two governing questions of hormonal function and malignant potential, and the imaging and biochemical features used to characterise a mass. It is a reference topic and does not provide surveillance schedules or individualised management advice.

Core questions

• Does the adrenal mass autonomously secrete a hormone such as cortisol, aldosterone, or catecholamines (is it functioning)?
• Are the imaging characteristics and size suggestive of a benign adenoma or of malignancy?
• How should the small subset of masses with concerning features be distinguished from the large majority that are benign and non-functioning?

Key concepts

• Adrenal incidentaloma
• Functioning versus non-functioning mass
• Benign adenoma versus adrenocortical carcinoma
• Autonomous (subclinical) cortisol secretion
• Imaging phenotype (lipid content and washout characteristics)
• Hormonal work-up of an adrenal mass
• Adrenal metastasis from extra-adrenal cancer

Mechanisms

Most incidentally found adrenal masses are benign, non-functioning cortical adenomas, but a minority secrete hormone autonomously or are malignant. Functioning lesions produce disease by the hormone they secrete: cortisol-secreting adenomas can cause overt or mild autonomous cortisol excess, aldosterone-secreting adenomas can cause primary aldosteronism, and medullary tumours can secrete catecholamines. Malignancy risk is signalled chiefly by larger size and by imaging features reflecting tissue composition, since benign adenomas are typically lipid-rich while carcinomas and metastases are not. The two-axis evaluation, hormonal function and malignant potential, therefore combines biochemical testing with characterisation of the mass on imaging.

Clinical relevance

Adrenal incidentalomas are common findings of cross-sectional imaging, so the framework for sorting the benign and non-functioning majority from the few that secrete hormone or are malignant is widely relevant. This entry presents that conceptual framework; it is not a basis for deciding on follow-up imaging, biopsy, or surgery, which require clinical evaluation.

Epidemiology

Adrenal masses are found in a few percent of abdominal cross-sectional imaging studies, and their prevalence rises with age. The large majority are benign, non-functioning cortical adenomas; adrenocortical carcinoma is rare, and the probability of malignancy rises with the size of the mass.

Evidence & guidelines

The European Society of Endocrinology, in collaboration with the European Network for the Study of Adrenal Tumors, published a clinical practice guideline on the management of adrenal incidentalomas (Fassnacht and colleagues, 2016) that frames the dual assessment of hormonal function and malignant risk.

History

The adrenal incidentaloma emerged as a distinct clinical problem with the widespread use of computed tomography and other cross-sectional imaging in the late twentieth century, which began revealing adrenal masses in patients imaged for unrelated reasons. This prompted a body of work, consolidated in later guidelines, on how to evaluate such masses systematically.

Key figures

• Martin Fassnacht

Seminal works

• fassnacht-2016

Frequently asked questions

What is an adrenal incidentaloma?

It is an adrenal mass found unexpectedly on imaging performed for some other reason, with no prior suspicion of adrenal disease. Most are benign and non-functioning, but evaluation focuses on the minority that secrete hormone or could be malignant.

What two questions guide the evaluation of an adrenal mass?

Whether the mass secretes a hormone (is it functioning), assessed by biochemical testing, and whether it is benign or malignant, assessed largely by its size and imaging characteristics.