Which characteristic distinguishes a malignant tumor from a benign tumor?

A malignant tumor is primarily distinguished by its potential to metastasize. This means that malignant tumors have the ability to invade nearby tissues and spread to distant organs through the bloodstream or lymphatic system. This capability to establish secondary tumors is a defining feature of malignancy and is what makes these tumors particularly dangerous and difficult to treat.

In contrast, benign tumors typically do not have this capacity for metastasis. They are usually well-defined, surrounded by a capsule, and do not infiltrate surrounding tissues. While benign tumors can grow and may cause problems by pressing on nearby structures, their inability to spread throughout the body is a key factor that sets them apart from malignant tumors.

The other characteristics, such as slow growth, non-invasive nature, and uniform cell type, may describe some benign tumors but can also be observed in some malignant tumors under specific conditions. However, the potential for metastasis is the hallmark characteristic that unequivocally defines and differentiates malignant tumors from benign ones.