An uncommon adrenal incidentaloma

A 66-year-old man, with no significant past medical history, presented with an episode of macroscopic haematuria. The physical examination showed no abnormalities, there was no flank pain, urinalyses was normal and the patient stated it was a single episode. CT was requested for further investigation.

Although CT urogram is warranted to study a gross haematuria episode, only an unenhanced abdominal CT was requested, mainly to discard urolithiasis as a cause for haematuria. Unenhanced CT depicted a 5,5cm left adrenal mass with attenuation measuring 18 HU, non consistent with a lipid-rich adenoma (Fig. 1). An MRI was requested which depicted no areas of high signal intensity on T1-weighted images and no signs of chemical shift, namely no signal dropout on opposed-phase T1-weighted imaging (Fig. 3). On MRI, the mass shows predominantly a multicystic morphology with high signal intensity on T2-weighted imaging (Fig. 2), high ADC values (Fig. 4), thick walls and multiple septa. After intravenous gadolinium-contrast administration there is avid wall and septa enhancement (Fig. 5). Both on CT and MRI there were no other abdominal noteworthy findings, namely there were no significant renal findings, the right adrenal gland was normal and there were no suspicious lymph nodes.

This adrenal mass has no typical features, both on CT and MRI imaging. Moreover, its multicystic appearance and contrast-enhancement raised the possibility for a pheochromocytoma but a 24-hour urine sample showed normal catecholamines values. The other two main differential diagnoses considered were adrenal cortical carcinoma and an adrenal metastasis of an unknown primary tumour. On a multidisciplinary meeting the patient was proposed for left adrenalectomy. Histopathological examination revealed a cortical brownish mass with cystic areas and multiple vascular structures in keeping with cavernous haemangioma. An adrenal incidentaloma is an unanticipated adrenal mass, not related to the original diagnostic inquiry, estimated to be present in approximately 4-5% of patients undergoing CT. Further diagnostic work-up is warranted for lesions ≥1cm, some of which can be readily diagnosed on imaging [1,2]. Most adrenal incidentalomas are adenomas (80%), two-thirds of which are lipid-rich adenomas that show attenuation less than 10 HU on unenhanced CT and chemical shift on MRI. Lipid-poor adenomas may still show chemical shift on MRI and specific values of washout on a contrast-enhanced scan with a delay of 60-90 sec and a delayed scan at 15 minutes [1,2]. Myelolipoma is an uncommon tumour that contains macroscopic fat recognised as areas of low attenuation on unenhanced CT (less then -10 to -20 HU). Diagnosis is confident if the fat content exceeds 50% of the mass to avoid pitfalls of myelolipomatous metaplasia in adrenal adenoma and adrenal carcinoma [2]. Simple cysts and calcifications can usually be readily documented on CT and/or MRI. Most other adrenal lesions, such as pheochromocytoma, adrenal carcinoma and metastasis have nonspecific features on both CT and MRI. When an incidentaloma has indeterminate features and the results of hormonal work-up are normal, there is an option for further imaging tests not yet performed, interval imaging in 6-12 months (non-enhanced CT or MRI) or adrenalectomy. Adrenal biopsy is usually not recommended [1]. Adrenal haemangiomas are extremely rare benign non-functioning vascular tumours (1 per 10.000 autopsies). They consist of two main types, cavernous and capillary, but the former is most frequent. CT may show phleboliths and both CT and MRI may depict a characteristic peripheral discontinuous nodular contrast enhancement, which can point to the correct diagnosis. Other findings show a thin rim wall and septa enhancement, as shown in our case, which is nonspecific and may be present in tumours such as adrenal metastasis and adrenal carcinoma [3,4]. The purpose of this presentation is to show some general rules to diagnose typical adrenal incidentalomas and to alert that an indeterminate mass may still be benign and further work-up, or even adrenalectomy, may be necessary to reach a diagnosis. Written informed patient consent for publication has been obtained.