Carcinoma in situ (CIS)

What does carcinoma in situ (CIS) mean?

Carcinoma in situ (CIS) is a diagnosis that describes an early non-invasive type of cancer. Without treatment, the cancer cells in CIS will eventually spread into the surrounding normal tissue. The movement of cancer cells into the surrounding tissue is called invasion.

How does carcinoma in situ start?

CIS starts with a single abnormal cell. As the abnormal cell divides it creates many more abnormal cells. Eventually the group of abnormal cells is large enough that they replace the normal, healthy cells.

CIS is called a non-invasive type of cancer for two reasons:

1. When examined under the microscope, the abnormal cells in CIS look very similar to cancer cells.
2. Unlike invasive types of cancer, the abnormal cells have not spread into the surrounding normal, healthy tissue.

Can carcinoma in situ spread to other parts of the body?

No. The cancer cells in CIS do not have the ability to spread to lymph nodes or distant parts of the body. The movement of cancer cells to another part of the body is called metastasis.

Types of carcinoma in situ

There are many different types of CIS and the type depends on where in the body the disease starts.

Some common types of CIS include:

• Squamous carcinoma in situ – Skin, mouth, larynx, lungs, cervix.
• Adenocarcinoma in situ – Cervix, lungs, gastrointestinal tract.
• Ductal carcinoma in situ – Breast.