Change in adrenal mass size as a predictor of a malignant tumor.

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.