Ductal Carcinoma in Situ (DCIS)
The list of differential diagnoses of calcifications on mammography is long and varied ranging from normal tissue to cancer. Most texts claim that if evaluated in detail, every breast will contain one or more calcifications, the vast majority of which are secondary to benign processes. Examples of benign calcifications include the following:
1. Skin calcifications: frequently have lucent centers
2. Vascular calcifications
3. Involuting or involuted fibroadenomas: â€śpopcornâ€ť-shaped calcifications
4. Non-specific coarse calcifications: irregular calcified debris in ectatic ducts
5. Rod-shaped â€śsecretoryâ€ť or linear calcifications
6. Round and smooth calcifications: represent fat-necrosis or ductal debris
7. Lucent-centered calcifications: secondary to fat-necrosis or secretory deposition
8. Rim or â€śeggshellâ€ť calcifications: calcification in the wall of a cyst or secondary to fat necrosis
9. Milk of calcium: curvilinear calcifications secondary to calcium precipitate in cysts
10. Suture calcifications: in areas of previous surgery (shaped like knots or sutures)
11. Dystrophic calcifications: large, irregular calcifications that usually remain unchanged over a period of several years representing dystrophic deposits
12. Punctate or â€śpinpointâ€ť calcifications: under 0.5 mm; usually benign secondary to sclerosing adenosis but may be present in DCIS
Due to the extensive differential diagnosis associated with the presence of calcifications and, because, when associated with malignancy, calcifications almost always indicate an intraductal cancer that may not be a threat for many years, some mammography experts have argued that too much emphasis is placed on the finding of calcifications. However, research has indicated that even the calcifications associated with low-grade DCIS may become advanced invasive cancers 10-20 years later. Thus, finding DCIS, represented as calcifications on mammography, will likely reduce the risk of mortality in the long term. Patterns of calcifications that are frequently associated with malignant processes include the following:
1. Pleomorphic calcifications: the greater the heterogeneity of the shapes of individual deposits, the greater the likelihood of cancer; though these may represent benign papillomas, DCIS, or invasive breast cancer this mammographic finding demands biopsy
2. Fine, linear branching calcifications: conform to a ductal distribution but are not solid rods or lucent-centered calcifications of benign secretory deposits; usually represent DCIS
The distribution of calcifications on mammography is also an important indicator of malignancy. Worrisome distributions include clustered calcifications, linearly distributed calcifications, or segmentally distributed calcifications. Patterns suggesting benign processes include regionally distributed or diffusely scattered calcifications as the more widespread the calcifications, the more likely they are to be due to a benign process. However, diffusely scattered calcifications make the finding of clustered calcifications more difficult for the mammographer.
A recent effort to differentiate the forms of DCIS (well-differentiated, moderately well-differentiated, or poorly differentiated) based on mammographic appearance has proven fruitless suggesting that in most cases trying to guess histology based on mammography is merely speculation. Only a very few types of calcification patterns are predictive and can be described with any degree of certainty.
Once the diagnosis of DCIS or other pre-cancerous or cancerous lesion is established by mammography, the case should be referred to general surgery for appropriate treatment and coordination of surgical, chemo- and radiotherapeutic modalities. For the patient currently in question, breast conservative measures have proven sufficient to halt the development of invasive cancer in the suspected lesion, however, due to her history of DCIS she would be considered to have a higher likelihood of developing other suspicious lesions.
Several studies are currently ongoing comparing the image quality and the radiation dose of digital mammography to that of more traditional methods. Cost-to-benefit ratios have also been examined for both techniques. Digital mammography allows for the separate optimization of image acquisition and display and opens the door for possibilities such as image processing, computer aided diagnosis, tomosynthesis, dual energy mammography, digital subtraction mammography, Sestamibi breast scintigraphy (may help identify drug resistant tumors), positron emission tomography, and telemammography, with the possibility of reducing radiation dose to the patient. However, it has not yet been firmly established as an improvement upon traditional breast imaging techniques.