A case of adrenal cortical carcinoma arising from a regularly monitored sub-centimetre adrenal incidentaloma.

Summary: Approximately 80% of adrenal incidentalomas are benign, and development into adrenal cortical cancer is extremely rare. This is a major reason behind clinical guidelines recommending surveillance of incidentalomas for a relatively short duration of up to 5 years. Surveillance of lesions less than 1 cm is not routinely recommended. A 70-year-old lady was diagnosed with a non-hyperfunctioning 8 mm right adrenal lesion. She underwent annual biochemical and radiological assessment for 5 years before surveillance was extended to 2-yearly intervals. The lesion was stable in size, and radiological characteristics were consistent with a benign adenoma. Seven years after the initial detection of the adrenal lesion, she developed acute abdominal pain. Imaging revealed a 7 cm right adrenal lesion, which was surgically resected and histologically confirmed to be adrenal cortical cancer. She died 1 year later. Clinical guidelines have moved towards a shortened duration of surveillance of incidentalomas. Even though malignant transformation is a rare event, it is possible that this will result in a delayed diagnosis of adrenal cortical cancer, a highly aggressive malignancy with a poor prognosis. To our knowledge, this is the first published case of an adrenal lesion of less than 1 cm developing into adrenal cortical cancer. Learning points: Adrenal incidentalomas are increasingly common. Clinical practice guidelines exist to aid in differentiating benign and malignant lesions and assessing functional status. Transformation of adrenal incidentalomas to adrenal cortical carcinomas is a rare but recognised event.