The Weiss score is the reference method to distinguish between a benign and a malignant adrenocortical tumor. It includes nine criteria. If a Weiss score is above 3 it means that the mass is cancerous and the diagnosis of ACC can be established. Scores of 2 and below define the adrenal adenoma (benign mass), even if sometimes a Weiss score of 2 can be suspicious. It is to be included in standard work-up of ACC patients, but is not used by every medical team or in every country.