They are classified as established by the international ONCO-RADS guidelines, which stands for Oncologically Relevant Findings Reporting and Data System:
- ONCO-RADS category 1: normal findings
- ONCO-RADS category 2: very likely benign findings
- ONCO-RADS category 3: probably benign findings
- ONCO-RADS category 4: probably malignant findings
- ONCO-RADS category 5: very likely malignant findings
