Adrenal masses falsely diagnosed as adenomas on unenhanced and delayed contrast-enhanced computed tomography: Pathological correlation

Abstract

Diagnosing adenoma merely on CT numbers can lead to misdiagnosis. The lower specificity than expected is due to pheochromocytomas presenting as false positives.

Multi-Detector-Row CT Diagnosis of Adrenal Incidentaloma in Patients with Hepatocellular Carcinoma

“…Although we did not find any clear definition in the literature of "lipidrich" or "lipid-poor" adenomas in terms of pre-contrast CT attenuation, previous researchers have investigated attenuation threshold values of 10 -25 HU when distinguishing adenomas from other masses on pre-contrast CT; in the past decade, a sensitivity of 36% -89% and a specificity of 95% -100% was reported [15][16][17][18][19][20]. Here, we adopted a pre-contrast CT attenuation value of 20 HU to define lipid-poor adrenal adenomas; lesions with less than 20 HU were excluded as these were considered typical lipid-rich adenomas (or some with negative HU, myelolipomas), and lesion with 20 HU or greater attenuation on noncontrast CT that were stable over 6 months or greater were judged to be lipid-poor adenomas.…”

Re-evaluation of pheochromocytomas on delayed contrast-enhanced CT: washout enhancement and other imaging features

“…The reason for this is the lack of overlap between the APEW and RPEW values of these two adrenal tumors. However, a few pheochromocytomas were reported to show early strong enhancement and rapid contrast material washout, which mimicked adenomas [5][6][7][8][9]. In particular, Park et al reported that the pheochromocytoma was the most common adenoma-mimicker, which reduced the diagnostic accuracy for adenoma using delayed contrast-enhanced CT [9].…”

“…On the other hand, there are several reports showing that a few pheochromocytomas had such high washout values on delayed contrastenhanced CT that they mimicked adenomas [5][6][7][8][9]. These studies included a small number of pheochromocytomas and did not adequately evaluate their imaging features of the CT images.…”

CT sensitivity for adrenal adenoma according to lesion size

“…Fourth, non-functioning adenomas were not included because lesions were diagnosed with the imaging study, not with biopsy or surgery. In addition, several non-adenomas with adenoma-like enhancement were not included in the analysis [14,26,27]. These false-positive lesions may decrease CT sensitivity for adenoma.…”

“…Adenoma may grow in a varying rate and adenocarcinoma focus may increase during a follow-up period. Pheochromocytoma or adrenal metastasis from renal cell carcinoma may grow as slow as adenoma, when the lesion is small (<3 cm) [14,26,27]. These non-adenomas Fig.…”