Which of the following best describes a malignant tumor?

A malignant tumor is best described as invasive and capable of metastasizing, which means it has the potential to spread from its original site to other parts of the body through the bloodstream or lymphatic system. This characteristic of malignancy distinguishes such tumors from benign tumors, which are localized and do not invade surrounding tissues or spread to distant sites. Malignant tumors are often aggressive, leading to various reproductive challenges, aggressive growth patterns, and the potential to cause significant health risks.

Understanding this concept is crucial in medical coding and documentation, as accurately coding for malignant conditions requires careful consideration of their potential for invasion and metastasis. The other options do not adequately capture the defining characteristics of malignant tumors; for instance, describing a tumor as benign or localized is contrary to the nature of a malignant tumor. Similarly, while surgery may be a treatment option for malignant tumors, it is not an absolute requirement in all cases, nor does it define the tumor itself.