Final answer:
The main difference between a malignant and nonmalignant tumor is the presence of cancer cells. Malignant tumors are cancerous and can invade neighboring tissues and spread to other parts of the body. Benign tumors, on the other hand, are localized and generally do not harm health.
Step-by-step explanation:
The main difference between a malignant and nonmalignant tumor is the presence of cancer cells. Malignant tumors are cancerous and contain cells that can invade and damage neighboring tissues. They can also break away and spread to other parts of the body through the bloodstream, forming new tumors. On the other hand, nonmalignant or benign tumors are localized and generally do not harm health.