Addressing how a tissue absorbs and releases the contrast agent used in computed tomography (CT) scans – called a wash-out analysis – may help researchers determine if a tumor in the adrenal gland is benign or malignant, especially in the case of cortisol overproduction.
This findings, reported in the study, “The computed tomography adrenal wash-out analysis properly classifies cortisol secreting adrenocortical adenomas,” appeared in the journal Endocrine.
In 4% to 10% of CT scans performed for any condition, masses greater than 1 cm in diameter are found in the adrenal glands. These masses are called incidentalomas, from the incidental nature of their discovery.
While incidentalomas are usually benign, they may represent conditions that require therapeutic intervention.
The structure and form of the adrenal lesion can provide some hints of its nature. A regular border, a maximum size in diameter less than 4 cm, and homogeneous tissue content suggests it is benign. However, these characteristics alone are not specific enough to accurately differentiate benign from malignant tumors.
CT scans require the administration of a contrast agent that is internalized by cells. Determining the amount of contrast retained by the tissues may help define the nature of the mass. However, adrenal masses often produce excess cortisol, and it is still unclear if cortisol secretion could influence the imaging features of adrenal lesions.
Therefore, a research team at the University Hospital of Nancy in France compared the imaging features of surgically removed adrenal lesions with their cortisol-secreting status, as well as with their tumor nature (benign or malignant), defined by tissue analysis.
Among the 75 patients included in the study, 52 had adrenocortical adenomas (ACA) – defined as benign – and 23 had adrenocortical carcinomas (ACC), defined as malignant.
A total of 34 ACA and nine ACC cases were detected by incidental imaging.
Cushing’s disease symptoms led to the diagnosis of 25 secreting adrenal lesions, 13 of them ACA and 12 of which were ACC. An analysis of cortisol secretion showed that 28 ACA cases and 12 ACC were biologically active.
Based on imaging scans, malignant masses were significantly larger than benign ones. However, larger tumors were not necessarily more aggressive, the team found.
The density of tissues is usually helpful in determining if a mass if malignant or not. Usually, tissues with a density greater than 10 HU – a measure of density – are deemed malignant. While all ACC cases were above this value, 77% of ACA cases were also above the threshold for malignancy. Of these, 60% were secreting high levels of cortisol, suggesting the analysis was not accurate for cortisol-producing tumors.
However, the wash-out analysis revealed that 85% of cortisol-secreting and 40% of non-secreting ACAs were in accordance with a benign classification.
The results show that while CT scans are highly sensitive in identifying malignant tumors, they lack specificity – because benign lesions are also identified as malignant.
But adding wash-out analysis to the evaluation significantly increased the sensitivity for benign tumors, particularly for those actively secreting cortisol.
“The relative adrenal [wash-out] analysis consolidates the benign nature of an ACA, especially in case of cortisol oversecretion,” the investigators concluded.