Endocrine Abstracts

Background: The prevalence of adrenal incidentalomas has increased. The malignancy is determined by radiographic appearance and, secondly, by the size. Adenomas manifest a low attenuation on computed tomography (CT) (<10 Hounsfield Units(HU)).The cut-off point of 10 HU has been proposed to discriminate benign and malignant lesions.

Objective: To determine if the cut-off point of 10 HU is useful in clinical practice to discriminate benign and malignant incidentalomas. Determine if there are other discriminatory characteristics.

Methods: Retrospective serie of patients referred for adrenal incidentaloma in imaging test between 2015–2019.The characteristics of incidentalomas by CT and other tests were evaluated and associated with the final diagnosis.

Results: Baseline characteristics are shown in Table 1. Of the 139 patients,3 were diagnosed of adenoma by magnetic resonance (MR). In the remaining 136,CT without contrast was performed and the results are shown in Table 2. Of the 27 lesions with CT>10 HU:9 were adenomas (false negatives of CT), 9 other diagnosis and 10 were lesions with uncertain malignant potential (UMP).

Finally, 8 patients (6%) were operated: 3 functioning adenomas and the rest corresponding to the UMP group: 1 pheochromocytoma (17UH), 1 hematoma (16UH), 1 cyst (>10UH), 1 metastasis (22UH) and 1 bleeding adenoma(>10UH). Of the 5 that were not operated,2 died during follow-up,1 decided not to continue the study and 2 are keeping under observation by PET-CT without hypermetabolism. No differences were observed depending on the size between the different lesions. Finally, there were 116 adrenal adenomas:12% were false negatives on CT without contrast using a 10 HU cut-off point. The sensitivity to detect adenomas was 88%.

Conclusions: CT without contrast is an adequate tool to typify adrenal lesions and confirm or rule out malignancy.

The 10 HU cut-off pointdiscriminates properly benign lesions from malignant/uncertain behavior.

The size was not discriminatory to differentiate benign or malignant lesions.

It should be considered not to request metanephrines in patients with a characteristic image of adenoma on CT because image’s diagnosis excludes that of pheochromocytoma.