What is the difference between maligant and a benign cancer?

Overall course.: There are many differences between benign and malignant tumors. A benign tumor is often well differentiated, looks almost normal, and does not spread. A malignant lesion is usually poorly differentiated, ominous looking, and spreads to other sites by blood, lymphatics, and directly. It has a very bad course, and results many times in death unless aggressive treatment is done.