If there is no enhancement, the lesion may be characterized as a benign lesion, such as a cyst or hemorrhage. Metastases from particular primary malignancies, namely hepatocellular carcinoma or clear-cell renal cell carcinoma, have been shown to mimic adenoma based on their washout values. In one study, 84% (16 of 19) of metastases from these two primary tumors would be falsely considered lipid-poor adenomas if washout characteristics alone were used [76]. The use of washout CT may increase accuracy of characterization compared with MRI. In one small study, washout CT was slightly superior to MR-CSI in characterizing adrenal masses measuring >10 HU on unenhanced CT [42]. Another study demonstrated that washout CT is more accurate than MR-CSI characterization of hyperattenuating adrenal masses, regardless of history of malignancy [43]. Routine abdominal CT without IV contrast often will provide definitive evidence of adenoma. Routine abdominal CT with IV contrast is rarely diagnostic and should not be considered for characterization of a known adrenal lesion. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET can be used to identify metastases in oncologic patients in various cancers [26,77-79]. FDG-PET is sensitive to metabolically active lesions, and metastases usually show greater uptake than benign lesions. In several studies, there have been a few false-positives with FDG-PET, lowering specificity to 85% in one study [80], but excellent sensitivity has been achieved [26,77-79]. False-negative scans have occurred in renal cell carcinoma metastases [64]. Adrenal Mass Evaluation SUVs are typically greater for metastatic disease [21]. However, mild activity can be seen in benign adenomas (typically less than background liver), thus potentially leading to false-positive interpretations. Studies have predominantly evaluated FDG-PET or FDG-PET/CT in the oncologic population. However, Tessonnier et al [44] evaluated 41 adrenal tumors in 37 patients who had no history of malignancy using FDG-PET/CT.
Adrenal Mass Evaluation. If there is no enhancement, the lesion may be characterized as a benign lesion, such as a cyst or hemorrhage. Metastases from particular primary malignancies, namely hepatocellular carcinoma or clear-cell renal cell carcinoma, have been shown to mimic adenoma based on their washout values. In one study, 84% (16 of 19) of metastases from these two primary tumors would be falsely considered lipid-poor adenomas if washout characteristics alone were used [76]. The use of washout CT may increase accuracy of characterization compared with MRI. In one small study, washout CT was slightly superior to MR-CSI in characterizing adrenal masses measuring >10 HU on unenhanced CT [42]. Another study demonstrated that washout CT is more accurate than MR-CSI characterization of hyperattenuating adrenal masses, regardless of history of malignancy [43]. Routine abdominal CT without IV contrast often will provide definitive evidence of adenoma. Routine abdominal CT with IV contrast is rarely diagnostic and should not be considered for characterization of a known adrenal lesion. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET can be used to identify metastases in oncologic patients in various cancers [26,77-79]. FDG-PET is sensitive to metabolically active lesions, and metastases usually show greater uptake than benign lesions. In several studies, there have been a few false-positives with FDG-PET, lowering specificity to 85% in one study [80], but excellent sensitivity has been achieved [26,77-79]. False-negative scans have occurred in renal cell carcinoma metastases [64]. Adrenal Mass Evaluation SUVs are typically greater for metastatic disease [21]. However, mild activity can be seen in benign adenomas (typically less than background liver), thus potentially leading to false-positive interpretations. Studies have predominantly evaluated FDG-PET or FDG-PET/CT in the oncologic population. However, Tessonnier et al [44] evaluated 41 adrenal tumors in 37 patients who had no history of malignancy using FDG-PET/CT.