A large incidental adrenal mass – does size matter?

PC Eng, E Mills, J Webster, N Duncan, E Hui, Northwick Park Hospital, London North West Healthcare NHS Trust.

Introduction: The presentation of an incidentally found adrenal mass has become increasingly common due to advances in imaging techniques and may potentially raise concerns to patients. The size of the incidentaloma is one of the criteria for surgical consideration after hormonal evaluation. Masses larger than 4 cm in diameter without a clear-cut diagnosis has been recommended for consideration of adrenalectomy. The cutoff of 4 cm was associated with a 93% sensitivity and a 24% specificity for distinguishing between a malignant tumour and benign lesion.  However, an estimated 8 to 15% of the resected adrenocortical carcinoma (ACC) has a size of less than 5 cm and some benign lesions can be exceptionally large.

Case: We report a case of a 65-year-old man, with a past medical history of type 2 diabetes and presumed nephropathy. He underwent a MRA to exclude renal artery stenosis and was found to have an incidental right supra-renal mass measuring 7.5 x 7.5 cm in size. An enhanced CT chest/abdomen/pelvis was performed for further evaluation. It showed a well-circumscribed lipomatous mass and the appearance was consistent with an adrenal myelolipoma. Biochemical investigations suggested that the mass was non-secretory. These included a normal 24-hour urinary cortisol (34 nmol/24 hrs, NR 1-124 nmol//24 hrs, urine volume 2L/24hr), a suppressible morning cortisol of 49 nmol/L (NR < 50 nmol/L) following a 1-mg overnight dexamethasone suppression test, normal 24-hour urinary catecholamines, a aldosterone to renin ratio of 44 (<800 Conn’s unlikely). He was asymptomatic and did not have features of Cushing Syndrome. Despite a benign radiological appearance, he was referred to urology due to the large size of the mass. Following a review in the Urology MDT meeting, the options of adrenalectomy versus conservative management were discussed with the patient, who opted for surgery. He underwent an elective laparoscopic right adrenalectomy. The histology confirmed an adrenal myelolipoma and he made a good recovery.

Conclusion: ACC prevalence accounted for 2% of lesions < 4cm, 6% of lesions from 4.1 to 6 cm, and 25% of lesions > 6cm. However, adrenal size alone is not sufficient to distinguish between benign and malignancy.  Clinical, biochemical, and radiological evaluation of an incidental adrenal mass should be taken into account. Though conservative management is a reasonable option for benign adrenal lesions, some larger lesions may rupture or cause compressive symptoms on surrounding structures; hence surgical consideration for such patient is essential.