What would be a characteristic of malignant tumors?

Malignant tumors are characterized by their aggressive nature and ability to invade surrounding tissues. One key feature is their irregular shape and possible invasion of lymph nodes. This irregularity arises from the chaotic growth patterns of malignant cells, which can disrupt normal tissue architecture. Unlike benign tumors, which tend to be smooth and well-defined, malignant tumors can infiltrate adjacent tissues, making them less well-defined and more challenging to distinguish from surrounding structures.

The invasion of lymph nodes is particularly significant because it indicates a potential for metastasis, where cancer cells spread to other parts of the body through the lymphatic system. This ability to spread and invade is a hallmark of malignancy, distinguishing malignant tumors from benign tumors that typically do not metastasize and are often encapsulated.

The other options highlight characteristics more associated with benign tumors or the general progressive nature of tumors but do not accurately reflect the traits of malignant tumors. Encapsulation, for example, suggests contained growth, which is more typical of benign tumors.