Differential Diagnosis The differential diagnosis of adrenal masses should take several key factors in consideration, including demographics, mode of discovery, clinical, and biochemical presentation, presence of any genetic pre disposition syndrome, as well as imaging characteristics (Table 1). While prevalence of adrenal tumours in children is <0.5%, risk of malignancy is high, with up to 60– 80% represented by adrenocortical carcinomas. Overall, adrenocortical carcinoma represents 1.3% of all malignancies in patients younger than 20 years of age. Adrenal tumours discovered incidentally are less likely to be malignant or hormonally active in comparison to patients presenting with symptoms suggestive of hormone excess or undergoing imaging for the purposes of cancer staging. However, malignant tumours and pheochromocytomas are not infrequently discovered incidentally, as was reported in 42– 54% of large tumours, reflecting the non- specific of symptoms and/ or subclinical presentation of adrenal hormonal excess. See Table 2 and Figure 1.
Table1. Differential diagnosis of adrenal tumours
Table2. Key points on the differential diagnosis of adrenal incidentalomas: consider history, demographics, clinical presentation, adrenal mass imaging phenotype, and any presence of genetic predisposition syndromes
Fig1. CT images of (a) adrenocortical carcinoma, (b) phaeochromocytoma, and (c) metastases from extra- adrenal cancer.
Risk of malignancy increases with the size of the adrenal mass. In a multicentre study of 1096 patient with incidentally discovered adrenal tumours, sensitivity of tumour size cut- off of >4 cm to diagnose adrenocortical carcinoma was 93%, though specificity was only 42%. A higher cut- off of 6 cm improved specificity to 71– 73%, but at a cost of lower sensitivity of 61– 74%. In a large retrospective cohort of patient with adrenal tumours >4 cm, prevalence of malignancy was reported to be 31% (18% adrenocortical carcinoma and 13% other malignant tumours). Similarly, 20% of patients with adrenal tumours >4 cm were found to have adrenocortical carcinomas in a prospective cohort of patients.
