Malign is a medical term that refers to an abnormality or disorder that is cancerous, or has the potential to become cancerous. It is used to describe a wide variety of diseases, from benign tumors to aggressive tumors that spread quickly. Malignancy can range in severity, depending on how abnormal the cells are and how fast they are spreading. Malignancy can also refer to precancerous conditions that can be treated or monitored to prevent cancer from developing.