Pathology dictionary -
Carcinoma in situ
Carcinoma in situ is a diagnosis that describes an early non-invasive type of cancer. There are many different types of carcinoma in situ and the type depends on where in the body the disease starts.
Carcinoma in situ 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.
Carcinoma in situ is called a non-invasive type of cancer for two reasons:
When examined under the microscope, the abnormal cells in carcinoma in situ look very similar to cancer cells.
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 carcinoma in situ 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.
Why is this important? Without treatment, the cancer cells in carcinoma in situ will eventually spread into the surrounding normal tissue. The movement of cancer cells into the surrounding tissue is called invasion.
Types of carcinoma in situ
In many parts of the body, carcinoma is given a special name that describes the type of cells found in that part of the body.
Some common types of carcinoma in situ include:
Breast - Ductal carcinoma in situ (DCIS).
Cervix - High grade squamous intraepithelial lesion (HSIL).
Bladder - Urothelial carcinoma in situ.
Lung - Adenocarcinoma in situ (AIS).
Mouth - Squamous carcinoma in situ.