Malignancy refers to the presence of cancerous cells that can grow uncontrollably and invade nearby tissues. Unlike benign tumors, which are non-cancerous and do not spread, malignant tumors can metastasize, meaning they can spread to other parts of the body through the bloodstream or lymphatic system. The term is often associated with various types of cancer, such as breast cancer, lung cancer, and leukemia. Early detection and treatment are crucial for improving outcomes, as malignancies can lead to serious health complications if left untreated.