A patient suffering from breast cancer chooses to undergo surgery. Doctors remove the breast where the tumor is. However, doctors say that there is no guarantee the cancer will not come back. What makes it so hard to cure cancer? Check all that apply.

A single cancer cell left behind after surgery can multiply and form a new tumor, so removing the breast does not always remove every cancer cell. Cancer cells can also travel through the blood and establish tumors in other parts of the body. Because many cancer cells multiply rapidly, tumors can grow or return quickly. Choice C is incorrect: research into cancer treatments and possible cures is ongoing.

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