Objective: To assess the value of adrenal mass absolute growth, growth rate, and percentage growth rate on serial imaging for distinguishing benign from malignant adrenal masses.
Methods: We retrospectively reviewed the Cleveland Clinic medical record data on 136 adrenalectomies or biopsies in 132 patients with 2 imaging studies performed more than 2 months apart (during 1997 to 2008).
Results: There were 111 benign (81.6%) and 25 malignant (18.4%) adrenal masses. With use of receiver operating characteristic curve analysis, all 3 aforementioned growth measures showed similar levels of discrimination for the entire study group as well as for the subgroups with 3 to 12 months of follow-up (n = 75 masses) and noncontrast computed tomography Hounsfield units >10 or not reported (n = 111 masses). After adjustment for other factors, the 3 growth measures remained statistically significant predictors of a malignant tumor. The absolute growth cutoff value of 0.8 cm had the highest sum of sensitivity and specificity of 72% and 81.1%, respectively. We could not identify an adrenal mass growth cutoff value to provide 100% sensitivity or specificity to confirm or exclude the presence of a malignant lesion. In 3 patients with metastatic lesions, no growth or a decrease in mass size during a period of 4 to 36 months was observed.
Conclusion: In this study, the largest with surgical histopathology findings as the "gold standard" for diagnosis, change in adrenal mass size was a significant predictor of a malignant tumor. Nevertheless, we could not identify an adrenal mass growth cutoff value for reliable confirmation or exclusion of a malignant lesion. Change in adrenal mass size should be used in conjunction with other imaging and clinical characteristics when surgical resection is being considered.