Is adrenal adenoma to carcinoma transformation possible?

A minority of adrenocortical carcinomas (ACC) demonstrate indolent growth, but can usually be identified by radiological characteristics such as inhomogeneity or high unenhanced density. However, cases of ACC developing from a lesion with benign radiological features at baseline and histopathological reports of ACC embedded within an adrenal adenoma have emerged. The adenoma to carcinoma transition in the adrenal gland may be a possible, albeit rare, phenomenon. Case Descriptions We present two cases from two tertiary centres in the UK who were diagnosed with an adrenal adenoma and showed stable radiological characteristics over 14 years and 11 years respectively, prior to a rapid enlargement of the lesion and diagnosis with ACC. We review the existing literature and describe four additional cases who met radiological criteria for an adrenal adenoma and demonstrated prolonged lesion stability (>5 years) on serial imaging prior to a subsequent diagnosis of ACC. We also identify four case reports of patients with radiologically indeterminate adrenal nodules at baseline who demonstrated prolonged size stability for up to 10 years prior to an accelerated growth phase and diagnosis with ACC. There was no significant difference in the average time to ACC diagnosis seen in those with benign radiological features at baseline (10.5 years, n=6) and those with radiologically indeterminate nodules at baseline (8.75 years, n=4, p=0.39). Conclusions Adrenal lesions with baseline benign radiological characteristics can very rarely transpire to be ACC. Prolonged dimensional stability cannot be considered a reassuring feature in isolation when assessing radiologically indeterminate adrenal lesions.