Carcinoma in situ (
CIS), also known as
in situ neoplasm, is a group of abnormal cells. While they are a form of
neoplasm there is disagreement over whether CIS should be classified as
cancer. This controversy also depends on the exact CIS in question (i.e. cervical, skin, breast). Some authors do not classify them as cancer, however, recognizing that they can potentially become cancer. Others classify certain types as a non-invasive form of cancer. The term "
pre-cancer" has also been used.