Risk assessment in 457 adrenal cortical carcinomas: How much does tumor size predict the likelihood of malignancy?

BACKGROUND: Laparoscopic adrenalectomy for tumors > 6 cm is controversial because of the risk of malignancy, but data to support this position are mostly from small series. The recent NIH consensus conference did not make a definitive recommendation about management of 4- to 6-cm nonfunctioning incidentalomas. STUDY DESIGN: Adrenocortical carcinomas (ACC) recorded in the Surveillance, Epidemiology, and End Results (SEER) database (1988 to 2000) were compared with benign functional or nonfunctional adrenal cortical adenomas (excluding aldosteronomas) operated on at our institution between January 1, 1993, and July 1, 2003. Data were compared using t-tests, chi-square tests, likelihood ratios, and receiver operating characteristic (ROC) curves. RESULTS: We identified 457 patients with ACC and 47 patients with adrenal cortical adenomas; 376 and 44 neoplasms, respectively, had tumor size data available. Tumor size was larger in ACC 12.0 +/- 5.6 versus 4.2 +/- 1.9 cm, mean +/- SD, p < 0.05). For ACC presenting with local disease, the sensitivity specificity, and likelihood ratios of tumor size to predict malignancy were 96%, 52%, and 2.0, respectively, for tumors >= 4 cm; 90%, 80%, and 4.4 for tumors >= 6 cm; 77%, 95%, and 16.9 for tumors >= 8 cm; and 55%, 98%, and 24.4 for tumors >= 10 cm. Assuming a pretest probability of malignancy of 5%, the likelihood ratios derived from this study yield a posttest probability of 10%, 19%, and 47% for cancer in adrenal cortical tumors >= 4 cm, >= 6 cm, and >= 8 cm, respectively. CONCLUSIONS: These data suggest that size is useful for predicting malignancy, and that at a size threshold of >= 4 cm, the likelihood of malignancy doubles (to 10%) and it is more than ninefold higher for tumors >= 8 cm (47%).