RGD uses the Human Disease Ontology (DO, https://disease-ontology.org/) for disease curation across species. RGD automatically downloads each new release of the ontology on a monthly basis. Some additional terms which are required for RGD's curation purposes but are not currently covered in the official version of DO have been added. As corresponding terms are added to DO, these custom terms are retired and the DO terms substituted in existing annotations and subsequently used for curation.
The edges of tissue removed in a surgery for assessment of the effectiveness of a surgical procedure in achieving the local control of a neoplasm and the adequacy of tumor removal. When the margin is negative or not involved by tumor (e.g., CANCER) it suggests all of the tumor has been removed by the surgery.