Carcinoma in Situ

Synonyms

In Situ Carcinoma

Definition

CIS is a lesion that exhibits the cytologic changes of invasive carcinoma but that is limited to the epithelium with no invasion of the basement membrane. For instance, in colorectal cancer, it represents an early form of carcinoma that is restricted to the colon mucosa and only locally expands within the mucosa without expanding over the mucosa limits. There is a complete absence of invasion of the surrounding tissues. However, becoming bigger, CIS will then grow over the colon mucosa limits, reach the surrounding vessels and thus become invasive. Invasive carcinomas, that are able to metastasize, are often the first clinical presentation of colon cancer. Transitional cell CIS carries a high risk of progression to invasion. CIS is also found in breast cancer and cervical cancer.