In a study of 1,049 incidental adrenal masses in patients with no known history of cancer, none were malignant. The majority of lesions were adrenal adenomas, myelolipomas, and cysts [6]. 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 patients with cancer. However, Tessonnier et al [44] evaluated 41 adrenal tumors in 37 patients who had no history of malignancy using FDG-PET/CT. All tumors were without diagnostically benign features on CT or MRI. In this small series, a tumor/liver SUVmax ratio >1.8 yielded 100% sensitivity and specificity for malignancy. It is recognized that FDG-PET is less sensitive and specific for lesions <10 mm [25], and although PET has the potential to detect very small adrenal metastases, one study showed that 2 of 5 lesions that proved to be false- negative for malignancy on PET were <10 mm [26]. Therefore, the specificity of FDG-PET for characterizing adrenal lesions <10 mm may be limited. Image-Guided Biopsy Adrenal Gland For lesions measuring 1 to 2 cm and no history of malignancy, there is no primary evidence supporting the use of biopsy for initial evaluation [27-30]. Most studies on the efficacy of adrenal biopsy have been performed in a mixed population of patients. Biopsy samples insufficient to make a diagnosis are obtained in 4% to 19% (mean = 15%) of cases [7,45-47]. When sufficient material is obtained, the accuracy of biopsy is between 96% and 100% for malignant lesions. In one study, rates of positive biopsy in three groups with prior diagnosis of cancer, those with previously undiagnosed cancer with simultaneous masses suspicious for metastases, and those with isolated incidentalomas showed positive biopsy results of 70.6%, 69.0%, and 16.7%, respectively. In all three groups, size was a significant predictor of malignancy.
Adrenal Mass Evaluation. In a study of 1,049 incidental adrenal masses in patients with no known history of cancer, none were malignant. The majority of lesions were adrenal adenomas, myelolipomas, and cysts [6]. 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 patients with cancer. However, Tessonnier et al [44] evaluated 41 adrenal tumors in 37 patients who had no history of malignancy using FDG-PET/CT. All tumors were without diagnostically benign features on CT or MRI. In this small series, a tumor/liver SUVmax ratio >1.8 yielded 100% sensitivity and specificity for malignancy. It is recognized that FDG-PET is less sensitive and specific for lesions <10 mm [25], and although PET has the potential to detect very small adrenal metastases, one study showed that 2 of 5 lesions that proved to be false- negative for malignancy on PET were <10 mm [26]. Therefore, the specificity of FDG-PET for characterizing adrenal lesions <10 mm may be limited. Image-Guided Biopsy Adrenal Gland For lesions measuring 1 to 2 cm and no history of malignancy, there is no primary evidence supporting the use of biopsy for initial evaluation [27-30]. Most studies on the efficacy of adrenal biopsy have been performed in a mixed population of patients. Biopsy samples insufficient to make a diagnosis are obtained in 4% to 19% (mean = 15%) of cases [7,45-47]. When sufficient material is obtained, the accuracy of biopsy is between 96% and 100% for malignant lesions. In one study, rates of positive biopsy in three groups with prior diagnosis of cancer, those with previously undiagnosed cancer with simultaneous masses suspicious for metastases, and those with isolated incidentalomas showed positive biopsy results of 70.6%, 69.0%, and 16.7%, respectively. In all three groups, size was a significant predictor of malignancy.