Whether diffusion-weighted MRI techniques are helpful in distinguishing benign and malignant masses in various organ systems has been investigated. Neither Miller et al [61] nor Tsushima et al [62] found that this technique could differentiate adrenal adenomas and nonadenomas. For the diagnosis of adenoma, contrast-enhanced MRI does not provide additional information beyond the unenhanced technique. However, MRI without and with IV contrast may be considered if there is concern for pheochromocytoma, as the contrast can show the typical bright enhancement of this lesion. Contrast can also confirm lack of enhancement of a cystic lesion. Adrenocortical carcinomas can be functioning or nonfunctioning. Those with nonfunctioning tumors most often present with a large mass and symptoms such as abdominal or flank pain. Because of the typically late presentation of nonfunctioning tumors, metastatic disease is common. For those smaller masses discovered incidentally and as functioning tumors, which most likely present with Cushing syndrome or virialization, metastatic disease at the time of presentation is less likely [66]. Adrenal Mass Evaluation One study by Herrera et al [5] examined 342 patients without a history of malignancy and found that although the rate of malignancy in all adrenal nodules was only 1.5%, all malignant lesions were >5 cm. In a series of 887 patients who had adrenal incidentalomas, a diameter >4 cm was shown to have 90% sensitivity for the detection of adrenocortical carcinoma but low specificity, as only 24% of lesions >4 cm in diameter were malignant [27]. In contrast, in patients with a history of malignancy, Candel et al [11] found that 87% of lesions <3 cm were benign and that >95% of lesions >3 cm were malignant. In a similar population, Lee et al [35] found that 79% of lesions <2.5 cm were benign. Van Erkel et al [67] in a mixed population showed that a threshold of 3.1 cm discriminated 93% of lesions.
Adrenal Mass Evaluation. Whether diffusion-weighted MRI techniques are helpful in distinguishing benign and malignant masses in various organ systems has been investigated. Neither Miller et al [61] nor Tsushima et al [62] found that this technique could differentiate adrenal adenomas and nonadenomas. For the diagnosis of adenoma, contrast-enhanced MRI does not provide additional information beyond the unenhanced technique. However, MRI without and with IV contrast may be considered if there is concern for pheochromocytoma, as the contrast can show the typical bright enhancement of this lesion. Contrast can also confirm lack of enhancement of a cystic lesion. Adrenocortical carcinomas can be functioning or nonfunctioning. Those with nonfunctioning tumors most often present with a large mass and symptoms such as abdominal or flank pain. Because of the typically late presentation of nonfunctioning tumors, metastatic disease is common. For those smaller masses discovered incidentally and as functioning tumors, which most likely present with Cushing syndrome or virialization, metastatic disease at the time of presentation is less likely [66]. Adrenal Mass Evaluation One study by Herrera et al [5] examined 342 patients without a history of malignancy and found that although the rate of malignancy in all adrenal nodules was only 1.5%, all malignant lesions were >5 cm. In a series of 887 patients who had adrenal incidentalomas, a diameter >4 cm was shown to have 90% sensitivity for the detection of adrenocortical carcinoma but low specificity, as only 24% of lesions >4 cm in diameter were malignant [27]. In contrast, in patients with a history of malignancy, Candel et al [11] found that 87% of lesions <3 cm were benign and that >95% of lesions >3 cm were malignant. In a similar population, Lee et al [35] found that 79% of lesions <2.5 cm were benign. Van Erkel et al [67] in a mixed population showed that a threshold of 3.1 cm discriminated 93% of lesions.