Detecting DCIS; the importance of finding malignant microcalcifications
DCIS, or ductal carcinoma in situ, means that malignant breast cancer has been identified, but is has not yet infiltrated the duct walls. It is often said that DCIS is ‘still contained‘ within the TDLU, which stands for terminal ductal lobular unit. DCIS is thought to represent between 20%-40% of all detected breast cancers. The rate at which DCIS progresses to invasive cancer is around 30% of all cases over a 10 year period.
‘High grade’ DCIS is almost always accompanied by microcalcifications, which underscores the importance of screening mammograms and microcalcification identification. About 58% of screen-detected DCIS is of a high grade.
Approximately 85% is of either high or intermediate grade, while less than half of low grade DCIS show microcalcifications. Clearly, microcalcifications showing on a screening mammogram have a high correlation with higher grade ductal carcinoma in situ. High grade DCIS will very likely progress to grade 2 or 3 invasive ductal carcinoma within 3-10 years, if not successfully identified and treated.
Staging and treatment options for high grade DCIS
There is no clear consensus at to what to do with DCIS. Evidence from microcalcifications and histological evaluation will give a better indication of cancer staging, aggressiveness and management.
Some argue that an intensive investigation of microcalcifications in search of ductal carcinoma in situ is too alarmist, resulting in over diagnosis. But in the long term, rigorous microcalcification analysis has been shown to lead to a significant reduction in mortality.
Surgical removal of a confirmed DCIS lesion is a likely course of action. In general, DCIS is a ‘unifocal‘ (found in only one place) disease, so there is little chance of ‘missing‘ other tumor sites. However DCIS lesions are not always on one continuous mass. ‘Extensions‘ (little off-shoots of malignant cells) may be continuous or discontinuous with the main mass, at about a 50/50 rate.
Gaps of normal tissue between discontinuous segments can be in excess of 10 mm in up to 8% of cases. To be safe, a resection margin at surgery of at least 2 mm is preferred. In some cases, mastectomy is an option with DCIS, as well as radiotherapy (probably a page here on treatment and management options for dcis, with the reference below, especially clinical trials of tamoxifen).
A sentinel lymph node biopsy is usually not performed with DCIS. This is because the rate of positive axillary lymph node metastasis is extremely rare at this stage, with a rate of about 0.4%.
Diagnostic investigation using immunohistochemistry suggest a significantly higher rate of lymph node metastasis, at around 8%, but this is most often attributed to a ‘microinvasion‘ and not a typical DCIS.
Essentially, DCIS-MI or ‘with microinvasion‘ means that just a few tumor cells may have infiltrated the periductal stroma. Sometimes this minimal ‘infiltrating‘ status is not initially detected at first screening.
The Van Nuys Pronostic Index (VNPI)
Treatment options for DCIS are sometimes evaluated using the Van Nuys Prognostic Index (VNPI). It assesses the risk of recurrence on a scale of 1 to 3 and considers diagnostic factors such as the tumor size, width of resection margins, presence of necrosis (dead cells and debris), and nuclear grade. A woman’s age is also taken into consideration (in the updated version, not the original).
For further reading, I recommend you visit this page on DCIS as well as this page on Microcalcifications.
Here are a bunch of common Q&A…
- How is ductal carcinoma in situ found? DCIS is usually found during a mammogram done as part of breast cancer screening or when there is another concern with a woman’s breast. The rate at which DCIS is diagnosed has increased dramatically over the recent years, not because the DCIS is becoming more common, but because the mammogram technology can see the microcalcifications better.
- Is ductal carcinoma in situ life threatening? No, but it does require treatment to prevent the condition from becoming invasive.
- How is ductal carcinoma in situ treated? Most women with DCIS are effectively treated with breast-conserving surgery and some get radiation too.
- What are the ductal carcinoma in situ symptoms? DCIS sometimes can cause signs and symptoms such as a breast lump and/or blood nipple discharge. However, it doesn’t cause any signs or symptoms in most cases.
- What does ductal carcinoma in situ look like on a mammogram? It appear as clusters of calcifications that have irregular shapes and sizes.
- What causes ductal carcinoma in situ? It is not clear what causes DCIS. It forms when genetic mutations occur in the DNA of breast duct cells. The genetic cell mutations cause the cells to appear abnormal, but the cells do not yet have the ability to break out the breast duct.
- What triggers ductal carcinoma in situ? Researcher’s don’t know exactly what triggers the abnormal cell growth that leads to DCIS. It is most likely that a number of factors may play a part, including genes passed to you from your parents, your environment and your lifestyle.
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