Diagnostic performance of adrenal CT in the differentiation of adenoma and pheochromocytoma

Abstract

Background Differentiation of adenoma and pheochromocytoma on computed tomography (CT) may be problematic. Purpose To investigate if adenoma and pheochromocytoma can be differentiated with adrenal CT. Material and Methods A total of 147 pathologically proven adrenal masses (119 adenomas, 28 pheochromocytomas) that had undergone adrenal CT were retrospectively evaluated. Lesion attenuation on unenhanced phase (UEP), portal phase (PP), 15-min delayed phase (DP), absolute/relative percentage enhancement wash-out (APEW/RPEW), and qualitative features were recorded. Student’s t-test for parametric data, Mann–Whitney U test for non-parametric data, and Fisher’s exact test for categorical data were used. Diagnostic performance of CT attenuation was assessed by area under the curve (AUC) of the receiver operating characteristics. Results APEW of adenomas was not significantly different from pheochromocytomas; 68.4% and 59% ( P = 0.284). Adenomas had significantly higher RPEW; 57.3% vs. 37.4% ( P = 0.004). Of pheochromocytomas, 50% met APEW >60% or RPEW >40% criteria, and therefore were misclassified as adenoma on wash-out CT. Of those, 80% (4/5) were < 3 cm. UEP, PP, and DP attenuations of pheochromocytomas were significantly higher than adenomas; however, they were overlapping. AUC for UEP, PP, and DP was 0.906, 0.784, and 0.926, respectively. Larger pheochromocytomas were more likely to contain necrosis compared to smaller pheochromocytomas and adenomas; 41.6% vs. 12.5% vs. 3%. Homogeneous enhancement was seen in 25% of pheochromocytomas and 49% of adenomas ( P = 0.018). No significant difference was found in terms of lesion borders and presence of fat/calcification ( P > 0.05). Conclusions A considerable percentage of pheochromocytomas, especially smaller ones, demonstrate adenoma-like wash-out on CT. Heterogeneous enhancement, higher attenuation, and necrosis are more suggestive of pheochromocytoma.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

“…In our study, adenomas showed an approximately 20% and 100% higher mean absolute enhancement and relative enhancement ratio, respectively, compared with hypervascular nonadenomas. Several previous studies have demonstrated equivalent or higher absolute enhancement in adenomas than in hypervascular nonadenomas (15,19,20,23,25,27,28,(31)(32)(33), while opposite results have also been observed in some investigations (A, B) an 84-year-old man with adrenal metastasis from hepatocellular carcinoma and (C, D) a 68-yearold man with lipid-poor adenoma. The lesions in both A and C had equivalent low unenhanced attenuation.…”

“…Studies have shown that hypervascular nonadenomas mimic adenomas at washout CT (19,(24)(25)(26)(27)(28). Therefore, similar concerns may exist for the relative enhancement ratio.…”

“…The diagnosis of pheochromocytomas and adrenocortical carcinomas was histopathologically confirmed, whereas hematomas and cysts were diagnosed with typical CT findings and interval follow-up. In this study, adrenal metastases from hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), pheochromocytomas, and adrenocortical carcinomas were categorized as hypervascular nonadenomas, which reportedly mimic adenomas at contrast-enhancement CT (19,(23)(24)(25)(26)(27)(28). In a prior study (29) on contrast-enhanced dual-energy CT that evaluated the diagnostic performance of virtual noncontrast attenuation and iodine density for differentiating adrenal adenomas from metastases, we reported on 36 patients included in the current study.…”

“…A total of 29 relevant articles from the literature were reviewed (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(14)(15)(16)19,20,(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). Sixteen studies provided data on both adenomas (n = 964) and nonadenomas mostly comprising metastases (n = 623), all of which showed higher absolute enhancement in adenomas than in nonadenomas (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)14,16,22,29,30) (Table E4 [online]).…”

“…Data in parentheses are numbers of adenomas, with 95% CIs in brackets. (15,19,20,23,25,27,28,(31)(32)(33); three studies (101 adenomas vs 43 pheochromocytomas, four cortical carcinomas, and 19 metastases from RCC or HCC) showed higher absolute enhancement in nonadenomas (24,26,34); and all 13 studies presented a higher relative enhancement ratio in adenomas than in hypervascular nonadenomas (Table E5 [online]).…”