All of the following are characteristics of benign tumors except:

A) grow slowly.
B) not encapsulated.
C) grow by expansion.
D) no cachexia.

Benign tumors are characterized by slow growth, expansion, and lack of cachexia. However, they are encapsulated, which distinguishes them from malignant tumors that tend to invade surrounding tissues. Therefore, the incorrect characteristic is "not encapsulated," making option B the correct answer.