What are the differences between a benign tumour vs a malignant tumour?

Aggresiveness: In general the terms malignant vs benign refer the tumor's propensity to extend out from the central tumor and metastasize to lymph nodes and through the circulation to other places. Some benign tumors (like fibroids) can still be troublesome and all patients with malignant tumors - like melanoma - need to have treatment options discussed.