title: Adrenal mass imaging with multidetector CT: pathologic conditions, pearls, and pitfalls.
abstract: The adrenal gland is involved by a range of neoplasms, including primary and metastatic malignant tumors; however, the most common tumor detected is the incidental benign adenoma. Although computed tomographic (CT) findings will not always yield a definitive diagnosis, attention to these findings provides a road map to guide image interpretation. Adenomas typically demonstrate rapid washout, which is defined as an absolute percentage washout (APW) of more than 60% and a relative percentage washout (RPW) of more than 40% on delayed images. Adrenocortical carcinoma typically has an RPW of less than 40%; however, large size and heterogeneity are more reliable indicators of the diagnosis than are washout values. Washout characteristics of pheochromocytoma are variable; in conjunction with high levels of dynamic enhancement, pheochromocytomas may mimic adenoma (ie, APW > 60%, RPW > 40%). Myelolipomas appear as well-defined masses with variable quantities of fat and soft tissue. After contrast material administration, metastases usually demonstrate slower washout on delayed images (APW < 60%, RPW < 40%) than do adenomas, although hypervascular metastases may enhance similarly to pheochromocytoma. Finally, a number of nonadrenal pathologic conditions have been reported to mimic adrenal masses at CT.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiologic Science, Johns Hopkins School of Medicine, 601 N Caroline St, Baltimore, MD 21287, USA. pjohnso5@jhmi.edu
authors.forename: Pamela T
authors.initials: PT
authors.lastname: Johnson
authors.forename: Karen M
authors.initials: KM
authors.lastname: Horton
authors.forename: Elliot K
authors.initials: EK
authors.lastname: Fishman
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D000311:Adrenal Glands / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014481:United States