The Weiss system for evaluating adrenocortical neoplasms: 25 years later.

The evaluation and categorization of adrenocortical neoplasms remain among the most challenging areas in adrenal pathology. The Weiss system, first introduced 25 years ago, provides specific guidelines for differentiating adrenocortical adenoma from adrenocortical carcinoma and is considered the standard for determining malignancy in tumors of the adrenal cortex. Considerable advances in the understanding of the pathology of adrenocortical neoplasia have occurred since delineation of the Weiss system, offering alternative approaches to the contemporary assessment of adrenocortical tumors.