Likelihood ratio of computed tomography characteristics for diagnosis of malignancy in adrenal incidentaloma: systematic review and meta-analysis

Abstract

PurposeTo propose an evidence based diagnostic algorithm using mass characteristics to determine malignancy in patients with adrenal incidentaloma by CTscan.MethodsA systematic review in Medline, Scopus, relevant reference books and desk searching was performed up to January 2016 with relevant reference checking. The summery estimates of sensitivity, specificity, positive and negative likelihood ratio of different characteristics were calculated in two groups of the articles investigating the cases without previous malignancy and the articles investigating the oncologic cases.ResultsThirty six articles were included in this study. In the first group with no history of malignancy a positive and negative LR of 3.1 and 0.13 in 4 cm threshold and positive and negative LR of 2.85 and 0 in 10HU density were found. In the second group with history of malignancy positive and negative LR of 2.3 and 0.27 in 3 cm threshold and positive and negative LR of 3.6 and 0.08 in 20HU density were resulted.ConclusionThe results retrieved in this study considering the limitations show that adrenal incidentaloma with a size less than 4 cm or a mass larger than 4 cm with density less than 10HU in the first group can be managed with imaging follow up. For masses larger than 4 cm with density more than 10HU another diagnostic procedure should be performed. In the second group an adrenal mass larger than 3 cm or less than 3 cm with density more than 20HU should go under operation. But masses smaller than 3 cm with less than 20HU density can be followed by imaging.

One-Stop Shopping: Dual-Energy CT for the Confident Diagnosis of Adrenal Adenomas

“…Of note, Nagayama et al used a cutoff value of 10 HU to confirm an adrenal adenoma. In our practice, we are confident that the vast majority of adrenal masses with attenuation between 11 and 20 HU can be confidently characterized as benign adenomas (10).…”

WFUMB position paper on the management incidental findings: adrenal incidentaloma

“…According to a more recent meta-analysis, the cut-off value of 40 mm for malignancy had an area under the curve of 0.92 with high sensitivity (91%), but limited specificity (71%). The pooled positive (3.1) and negative likelihood ratio (0.13) of this 40-mm cut-off value are neither confirmative nor exclusive for malignancy, so that further parameters are needed for a definitive diagnosis [39].…”

“…The descriptive features for benign AI are an oval or round shape, sharp margins and smooth contour, and homogeneous echo pattern (US) or density (CT). In conclusion, an approach combining size (<40 mm) and HU values (≤10 HU) excludes malignancy in almost all cases [39,44]. However, approximately 30% of benign adrenal adenomas are lipid-poor, with attenuation values of ≥10 HU [45].…”

“…Specific quadriphasic contrast-enhanced adrenal CT protocols with higher radiation exposure allow calculation of absolute and relative wash-out [10]. Earlier wash-out in fat-containing adenoma and delayed wash-out in metastasis is observed [39,46,47,52-54]. A combination of unenhanced CT and wash-out CT calculation with delayed phase acquisition at 15 minutes for adrenal lesions with attenuation values ≥10 HU was shown to provide high sensitivity and specificity for differentiating adenomas from non-adenomas (98% and 92%, respectively) [52].…”

“…With all imaging techniques, the typical imaging features of adrenocortical carcinoma and metastases are a size >40-60 mm, irregular shape, inhomogeneous echo pattern, calcifications and non-enhancing spontaneous hemorrhage necrosis. Metastases tend to be bilateral [39,55-57].…”