Thus far, we have been considering carcinomas as cancers that pose a threat to life because they are “invasive,” which means that they have the potential to metastasize to other parts of the body. A pathologist will usually include the term “invasive” or “infiltrating” in a pathology report to indicate this important aspect of the cancer. For example, a tumor of the larynx may show “invasive squamous cell carcinoma,” one from the stomach, “invasive adenocarcinoma,” or one from the breast, “infiltrating ductal carcinoma.”
The terms “invasive” or “infiltrating” will be used when the pathologist sees the cancer cells invading through the first tissue barrier underneath it.
The term “invasive” in a pathology report does not mean that a cancer has metastasized, only that it might have done so.
If a tumor biopsy shows invasive carcinoma, then a staging workup will be undertaken to determine if any cancer deposits can be found elsewhere in the body. This evaluation is often performed before surgical removal of the primary tumor but in certain cases may be performed afterward. The results of the staging workup determine the “extent of the disease” and whether surgery can remove or has removed all visible areas of involvement.
Not all carcinomas, however, are invasive. One class of carcinoma is considered “pre-invasive.” This type of cancer is called Carcinoma In-Situ (Latin for “in site” or “in place”). Under the microscope, carcinoma in-situ (CIS) does not penetrate the tissue barriers beneath it.
Although CIS cells are growing in the characteristic disorganized way that identifies the tumor as a cancer, they have not yet acquired the ability to metastasize – to break into surrounding tissues and gain access to the blood or lymph stream to spread to other parts of the body. CIS does not pose an imminent threat to life, but it can develop into invasive carcinoma over time and must be treated.
Most cases of CIS are surgically removed if detected, rendering the patient cured of the CIS and eliminating the possibility that invasive cancer will develop from that area of carcinoma in-situ. CIS is not treated with chemotherapy, but radiation and hormonal therapy may play a role in treatment, especially in breast cancer. The cure rate for CIS is almost 100 percent.
In addition to being an “early cancer” that is highly curable, carcinoma in-situ is also an indicator that the affected person is at an increased risk for the future development of cancer (both in-situ and invasive types). Therefore, after someone is treated for CIS, he or she should undergo regular surveillance testing to detect newly developing cancers at their earliest, most curable stages. In addition, CIS marks an important moment in the health of a patient: it is an ideal time to take advantage of cancer prevention measures or make lifestyle changes (related to smoking, diet, and exercise, discussed before) that help ward off the disease.
Carcinoma in-situ is most commonly encountered in the breast. The detection of ductal carcinoma in-situ (DCIS) of the breast has dramatically increased since mammography has replaced simple physical examination as the primary way in which breast cancer is detected today.
Mammography enables the detection of much smaller cancers than are found by physical examination alone, and an increasing number of these smaller cancers consist of DCIS rather than invasive breast cancer. Many women who develop DCIS are advised to take the drug tamoxifen for five years after DCIS is treated in order to prevent the future development of breast cancer.
Tamoxifen blocks the stimulating effects of estrogen on breast cells and reduces the future occurrence of both DCIS and invasive breast cancer. These cancer-reducing effects are experienced by both breasts, not just the one in which the DCIS is found.
Carcinoma in-situ is found in other parts of the body much more often than is widely recognized, in part because patients are usually told that they have, not CIS, but rather “a tumor that is the step before [invasive] cancer.” For example, CIS can be found in a bladder polyp that may call attention to itself by causing blood in the urine. To screen for cervical cancer, a Pap smear is performed, which may lead to a diagnosis of dysplasia or cervical intraepithelial neoplasia (CIN); the most severe form of dysplasia is CIN III, which is equivalent to carcinoma in situ.
Other areas in which CIS can be found include the colon, prostate, thyroid, oral cavity, testicle, anus, and lung. Interestingly, both carcinoma in-situ and invasive cancer are sometimes found in the same tumor, indicating that the invasive cancer grew out of the CIS. This stepwise development of cancer is discussed.
