Complication rates range from 8% to 12% and consist of bleeding, pneumothorax, infection, and anecdotes of tumor seeding of needle instability should a clinically unsuspected pheochromocytoma be biopsied. Careful correlation with clinical and endocrinological data is needed, combined with knowledge of other features, such as tumor size and imaging characteristics to distinguish adenoma from carcinoma due to the possibility of sampling error. Thus, biopsy is better suited to a population with a high risk of malignant lesions and is most useful when noninvasive imaging studies are negative or inconclusive. MRI Abdomen Qualitative and quantitative MRI methods have been used to attempt to distinguish between adenomas and nonadenomas. MR-CSI (in-phase and opposed-phase gradient-echo scans) relies on differentiating lesions by their relative lipid content, with malignant lesions having virtually no lipid [50]. This has been shown to be correct for 96% to 100% of the cases, depending on the study [51,52]. However, these studies were performed in a mixed population of patients with regard to their history of malignancy, so results may not be directly applicable to populations either with or without known malignancy. Several other authors have shown excellent results in characterizing masses in populations with incidentally detected adrenal masses using simpler CSI techniques [53- 55]. In cases in which the unenhanced CT attenuation measurement was between 10 and 30 HU (ie, indeterminate by CT), applying CSI can be discriminatory. In one study, 89% of adenomas with densities between 10 and 30 HU were correctly characterized by CSI [59]. Another study concluded that up to 60% of lesions misclassified by unenhanced CT attenuation measurements can be correctly characterized as adenomas by MR-CSI [53]. Gabriel et al [60] have demonstrated that even heterogeneous loss of signal is evidence of a benign lesion. Thus, MR-CSI may have better sensitivity and specificity than nonenhanced CT.
Adrenal Mass Evaluation. Complication rates range from 8% to 12% and consist of bleeding, pneumothorax, infection, and anecdotes of tumor seeding of needle instability should a clinically unsuspected pheochromocytoma be biopsied. Careful correlation with clinical and endocrinological data is needed, combined with knowledge of other features, such as tumor size and imaging characteristics to distinguish adenoma from carcinoma due to the possibility of sampling error. Thus, biopsy is better suited to a population with a high risk of malignant lesions and is most useful when noninvasive imaging studies are negative or inconclusive. MRI Abdomen Qualitative and quantitative MRI methods have been used to attempt to distinguish between adenomas and nonadenomas. MR-CSI (in-phase and opposed-phase gradient-echo scans) relies on differentiating lesions by their relative lipid content, with malignant lesions having virtually no lipid [50]. This has been shown to be correct for 96% to 100% of the cases, depending on the study [51,52]. However, these studies were performed in a mixed population of patients with regard to their history of malignancy, so results may not be directly applicable to populations either with or without known malignancy. Several other authors have shown excellent results in characterizing masses in populations with incidentally detected adrenal masses using simpler CSI techniques [53- 55]. In cases in which the unenhanced CT attenuation measurement was between 10 and 30 HU (ie, indeterminate by CT), applying CSI can be discriminatory. In one study, 89% of adenomas with densities between 10 and 30 HU were correctly characterized by CSI [59]. Another study concluded that up to 60% of lesions misclassified by unenhanced CT attenuation measurements can be correctly characterized as adenomas by MR-CSI [53]. Gabriel et al [60] have demonstrated that even heterogeneous loss of signal is evidence of a benign lesion. Thus, MR-CSI may have better sensitivity and specificity than nonenhanced CT.