An adrenal incidentaloma is a lesion larger than 1 cm in diameter, serendipitously discovered by radiologic examination.
Its prevalence is increasing, from 0.4% to 4% in the last reports, reaching 10% in te elderly patients.
The etiology of adrenal incidentalomas varies and includes benign and malignant lesions derived from the adrenal cortex, the medulla or of extra-adrenal origin. Some authors conclude that the prevalence of malignant and functional lesions is likely to be overestimated, mainly because of the higher prevalence of malignancy in surgical literature. Up to 80% of adrenal tumors are benign, with malignant lesions amounting to about 5%.
Two questions must follow the discovery of an adrenal mass: is it malignant? And: is it functioning?
Even though malignancy is an uncommon cause of adrenal incidentaloma a CT-scan or MRI may allow for a prediction of the histologic type of tumour. The use of a PET-scan may provide information on its function.
Adrenal biopsy is generally discouraged unless there is a history of extra-adrenal malignancy and additional criteria are fulfiled:
- The lesion is hormonally inactive.
- The lesion has not been conclusively characterized as benign by imaging.
- The therapeutic approach would be altered by knowledge of the histology.
While most adrenal incidentalomas are nonfunctional (89.7%) 10% to 15% secrete excess hormone amounts:
- Primary adrenal carcinoma 1.9%
- Metastases: 0.7%
- Subclinical Cushing’s syndrome: 6.4%
- Pheochromocytoma: 3.1%
- Primary aldosteronism: 0.6%
The functional presentation of the tumors helps to categorize them into three entities:
- Subclinical Cushing’s syndrome is the glucocorticoid secretory autonomy without clinical manifestations of Cushing’s syndrome. It is the most frequent hormonal abnormality detected in patients with adrenalomas.
- Pheochromocytoma: catecholamines-secreting tumors that arise from chromaffin cells of the adrenal medulla and the sympathetic ganglia are referred to as “pheochromocytomas“. The presence of a pheochromocytoma should be suspected in patients with severe hypertension, tachycardia, palpitations, cardiac arrhythmias, anxiety attacks, weight loss, or sweating.
- Aldosteronomas are rare (less than 1 percent) causes of adrenal incidentaloma. However, because the majority of patients with primary aldosteronism are not hypokalemic, all patients with hypertension and an adrenal incidentaloma should be evaluated by measurements of plasma aldosterone concentration and plasma renin activity.
Treatment of this tumor depends on the histology and should change if there is a unilateral tumour or if both adrenal glands are affected.
- Unilateral adrenal masses: All patients with documented pheochromocytoma and adrenocortical cancer should undergo prompt surgical intervention because untreated pheochromocytoma may result in significant cardiovascular complications. Alpha blockade should be prescribed before adrenalectomy. Patients with aldosterone-producing adenomas should be offered surgery to cure the aldosterone excess. Adrenal masses with either suspicious imaging phenotype or size larger than 4 cm should be considered for resection because a substantial fraction will be adrenocortical carcinomas.
- Bilateral adrenal masses: management of bilateral adrenal masses is different from that for unilateral masses. As an example, in cases of subclinical bilateral macronodular adrenal hyperplasia (BMAH), size is not an indication for surgery, as some can be as large as 5 to 10 cm, with insufficient hormone production to require surgery. Patients with bilateral adrenal masses should be investigated for congenital adrenal hyperplasia
Laparoscopic adrenalectomy has been associated with less pain, shorter hospitalization time, less blood loss, and faster recovery than open adrenalectomy. The latter is recommended for large (> 10 cm) adrenal masses including those benign imaging features, as the adrenal mass may be diagnosed as malignant on a definitive histologic review
Incidentalomas with a benign appearance may be followed up through another CT or MRI in 6 to 12 months’ time. Most experts would consider resecting any tumor that enlarges by more than 1 cm in diameter during the follow-up period. However, most adrenal masses that grow are not malignant.