Ductal Carcinoma In Situ - DCIS
What is ductal carcinoma in situ?
Ductal carcinoma in situ (DCIS) is an overgrowth of irregular-looking cells in a duct (the delivery system) of the milk glands of a breast. Sometimes these overgrowths can nearly fill the tiny space within a section of a milk duct. DCIS, which is often called stage 0 cancer or noninvasive cancer, was formerly included in statistics about cancer rates. However, DCIS differs from invasive cancer in two very important ways: it does not spread (metastasize) to other locations in the body, and it does not kill anybody. Therefore, cancer is probably not a good name for the condition, because it does not involve out-of-control growth or an immediate threat to life and health. DCIS is, however, a precancerous condition. A woman who has untreated DCIS is much more likely to develop invasive breast cancer over her lifetime.
What is the likelihood of developing invasive breast cancer after a DCIS diagnosis?
At present, the best estimate is that the risk of developing invasive cancer within 10 years of a diagnosis of DCIS (if untreated) is 10–25%, and that the risk of invasive cancer over several decades or a lifetime is 25–40%. However, these figures are uncertain. Women who have a small DCIS detected by mammography may have a different risk of invasive cancer than women who have had a DCIS detected by other means in the past. It would not be unreasonable to estimate the 10-year risk at 15% -- that is, 15% of women with DCIS would develop invasive breast cancer within 10 years of diagnosis. This figure is reasonable because the 10-year risk of invasive cancer after a diagnosis of atypical hyperplasia (a benign breast condition with which DCIS is sometimes confused) is about six percent, and the risk from DCIS should be higher than that.
How common is DCIS?
It is not clear how common DCIS is. Routine mammography has increased the rate of detection of DCIS considerably. However, that does not mean that DCIS occurs more frequently, just that it is diagnosed more frequently. In 1980, when few women sought routine screening, one in 1,000 women was diagnosed with DCIS during the decade around menopause. The diagnosis was usually made after a lump was found or when there was a discharge from the nipple. By 1992, when 60% of women age 40–65 got routine mammograms, one woman in 250 was diagnosed with DCIS over a 10-year period. Most cases were detected because of mammographic results alone: the cell changes caused no symptoms and were too small to feel. In 1997, DCIS was diagnosed at the rate of one per 200 women per decade. The cases of DCIS that are diagnosed may be only a fraction of the total number of DCIS lesions that exist at a point in time.
At present, DCIS is most often diagnosed when a mammogram indicates calcium deposits and a subsequent biopsy shows severe cell irregularities. However, since cell irregularities tend to fall along a gradation of severity ranging from benign to cancerous, a diagnosis of DCIS is always an interpretation. There is a fuzzy boundary between DCIS and atypical hyperplasia (a risk factor -- not a precancerous condition) at the low end of cellular irregularities, and another fuzzy boundary between DCIS and minimal invasive breast cancer (a real cancer -- not a precancerous condition) at the high end.
If one expert pathologist looks at tissue from a breast biopsy under a microscope, he or she might classify the tissue as DCIS. If a second expert pathologist looks at the same tissue, around one-third of the time he or she might call it something else. Pathologists who do not specialize in breast disease may disagree even more frequently than that. However, no matter how DCIS is defined, recognized, or diagnosed, everyone agrees that DCIS is an important risk factor for invasive breast cancer.
How does DCIS differ from lobular carcinoma in situ?
Both lobular carcinoma in situ (LCIS) and DCIS are noninvasive cancers of the breast. LCIS occurs in the lobes (where milk is created) of the milk glands, and DCIS occurs in the ducts (the delivery system) of the milk glands. LCIS is considered a general risk factor for cancer: the same impaired immune defenses that allow growth of LCIS might also allow creation of a cancer. As a result, women with LCIS are at a higher risk of developing cancer, but those cancers would not necessarily develop in the same location as the LCIS or even in the same breast. In contrast, DCIS is more than a general risk factor for cancer: it is a precancer. Because DCIS cells can transform into invasive cancer, those cancers tend to appear in the same location as the DCIS. The occurrence of DCIS is a red flag indicating that if an invasive cancer should develop, there is a good chance that it will be found in that tiny mass of irregular cells.
How is DCIS treated?
Through the mid-1980s, the most common treatment for DCIS was a total mastectomy. This is no longer the case. As the number of diagnoses of DCIS has increased, breast specialists have learned more about treating the condition. At present, the treatment of choice for most cases of DCIS is wide excision of the tumor (a lumpectomy), sometimes followed by radiation treatment.
Although not much was known about DCIS before 1985, the general agreement was that this disease was multicentric -- that is, scattered throughout the breast tissue. Physicians were taught that if a DCIS lesion was found, then other undetected DCIS lesions probably existed in the rest of the breast, and that most, if not all, of these lesions were on the fast track to becoming invasive cancer. Given these assumptions, the only reasonable option was to remove the entire breast before the cancer-in-process had a chance to appear. Because most known cases of DCIS resulted in mastectomy, little information was available about what happened if DCIS was untreated, or treated in a more conservative manner.
As more was learned about DCIS, it became apparent that many DCIS lesions never result in invasive cancer at all. If an invasive cancer develops, it generally appears in the same location where the DCIS was originally spotted. Hence, earlier theories were incorrect: DCIS cannot be interpreted as a multicentric disease of the breast. There might be more than one separate DCIS lesion in a particular milk duct, but DCIS is usually a single-duct disease.
After DCIS is treated, how likely is it to recur?
The 10-year risk of getting invasive breast cancer following the most successful DCIS surgery is nearly as low as the average 10-year risk for women who have no DCIS. This outstanding treatment outcome requires that:
- a surgeon who is experienced in the treatment of breast disease must perform the initial lumpectomy and/or re-excision
- an expert pathologist who has experience in DCIS and skill in three-dimensional imaging of tumors must examine the tissue
- the tumor must be surrounded by a wide margin (at least 10 mm, or about one-half inch) of healthy tissue between the nearest DCIS and the outer edge of the removed tissue
Is radiation therapy recommended for DCIS?
Radiation therapy is often recommended for prevention of the local recurrence of DCIS, as approximately half of these recurrences will include an invasive breast cancer. For DCIS lesions treated with breast-conserving surgery, radiation therapy postpones a local recurrence.
Sometimes it is just not possible to perform a lumpectomy for DCIS and leave wide, clean margins of normal cells around the DCIS in all directions. If a margin is clean (no DCIS exists at the outer edge of the removed tissue) but not entirely wide (some lesions are closer than 10 mm to the outer edge of the removed tissue), then radiation therapy reduces the average recurrence rate by around 25%.
Is chemotherapy used to treat DCIS?
Chemotherapy is not used to treat DCIS. Chemotherapy is used in invasive cancers to destroy any daughter cells that the immune system has failed to recognize. When there is no invasive cancer, there are no daughter cells. A DCIS lesion is generally contained entirely within one milk duct.
Is mastectomy recommended for DCIS?
Mastectomy is not usually recommended for DCIS. In most cases, mastectomy is recommended if there is recurrent DCIS following treatment. There are, however, two reasons for selecting mastectomy as a first-choice treatment for DCIS:
Lesion size If the DCIS lesion is large, taking up a sizable section of breast tissue, then mastectomy may be recommended. Since reduction of risk for invasive cancer requires the removal of all of the DCIS (plus one-half inch of healthy tissue around the DCIS), it could make more sense to remove a breast with extensive DCIS and to do an immediate reconstruction.
Patient choice Sometimes the very idea of a precancer is so distressing that a woman may prefer to avoid even a small chance of a local recurrence. If the breast is removed, then there isn't much local area in which a DCIS could come back. Even a mastectomy does not lower the risk of invasive cancer to zero, but it does reduce the 10-year risk to no more than that for the average for woman who has no DCIS.
How soon should treatment be sought after a DCIS diagnosis?
Where a woman has treatment for her DCIS matters a great deal more than how soon she schedules the treatment. If you are diagnosed as having DCIS, you may want to seek out a comprehensive breast cancer treatment center. The surgeon should be one who specializes in the treatment of breast disease and the pathologist should have experience in three-dimensional imaging techniques.
