PET in Differentiating Benign from Malignant Masses

More recently, PET has been suggested as a useful tool in the evaluation of the nonhyperfunctioning adrenal mass.

Although still preliminary, the results of multiple recent studies suggest that PET performed with fluorine-18 fluorodeoxyglucose (FDG) is highly accurate in differentiating benign from malignant lesions.

In general, malignant masses in the adrenal gland (and elsewhere) show increased uptake of FDG due to increased glucose utilization, but benign noninflammatory lesions show no evidence of increased FDG uptake (Figs).

Contrast-enhanced CT scan demonstrates a smooth-margin, low-attenuation right adrenal mass (arrow).

FDG PET scan shows normal activity in the kidneys (arrows) but no increasing activity in the right adrenal gland.

Nonenhanced CT scan demonstrates a right adrenal mass (arrow)

FDG-PET SPECT scan obtained at the same level shows increased activity in the right adrenal gland (arrow), a finding diagnostic of a metastasis.

Three recent studies demonstrated that FDG PET had 100% sensitivity and 80%–100% specificity for differentiating malignant from benign adrenal masses. If these results are corroborated, FDG PET could become part of the routine evaluation of the patient with a nonhyperfunctioning adrenal mass, especially since the study allows simultaneous whole-body imaging. PET may also be useful for localizing pheochromocytomas.