Which of the following statements about malignant tumor are correct?

A、Malignant tumors often surrounded by a connective tissue capsule
B、Malignant tumors are less well differentiated or completely undifferentiated
C、In malignant tumors, mitotic figures are rare and normal
D、Secondary changes such as bleeding and necrosis in malignant tumors are far less common

E、Malignant tumor invade neighboring tissues, and metastasize to different sites