Mammographic Analysis of Breast Calcifications

Chapter 3 Mammographic Analysis of Breast Calcifications

Analysis of breast calcifications is important because they may be the only sign of cancer. At histologic examination, 50% to 80% of breast cancers contain calcifications, but only a small percentage of cancers show calcifications on mammography. Calcifications form in breast cancers because of central necrosis of the tumor or from malignant cell secretions. Because cancers grow in breast ducts, the calcifications forming in these tumors often take on the form of the duct, resulting in the typical linear and branching malignant-type calcifications in cancers seen on mammograms.

Most mammograms show calcifications of some type. However, the vast majority of calcifications are due to benign processes. It is tricky to recognize cancer calcifications and distinguish them from the wide variety of common benign calcifications, but it can be done. A careful, systematic approach to the mammogram enables the radiologist to detect cancer-type calcifications. Once the calcification is found, the radiologist looks at the individual forms, the shape and location of the calcification cluster, and any changes over time to see if they point to the presence of cancer. This chapter presents a systematic approach to finding breast calcifications on mammograms, and then covers an approach to classifying breast calcifications into benign, malignant-appearing, or indeterminate categories.

Technique for Finding Calcifications

The radiologist first makes sure the mammograms are of high quality, which is essential to detect and analyze breast calcifications. Then, the radiologist looks at each standard film using a standard search pattern so that no part of the film is unseen. Some radiologists use a search pattern of parallel lines over the films, like someone mowing a lawn, as described by Dr. Roger J. Jackman, to make sure all parts of the film are covered. With screen-film mammography (SFM), the radiologist uses a bright light to illuminate the darker portions of the film so the calcifications are easier to see. On digital mammography, the radiologist adjusts the windows and levels on the mammography workstation to optimize image contrast and brightness to find calcifications more easily.

After viewing the mammograms at standard magnification, the radiologist then uses a hand-held magnifying lens to examine each film (for analog SFM); this enlarges the mammogram image and makes the calcifications easier to detect. For digital mammography, the radiologist magnifies the mammogram electronically to make calcifications bigger and easier to see. Digital mammogram-viewing protocols usually incorporate electronic magnification of each image as part of the viewing workflow.

If calcifications that need further evaluation are detected, the radiologist orders air-gap magnification mammograms done with a 0.1-mm focal spot. People often mistakenly think that magnifying the SFM with a magnifying glass or electronically magnifying digital mammograms on the workstation is the same as performing air-gap magnification mammograms. It is not the same. Hand-held or electronic magnifiers can enlarge the calcifications that appear on mammogram images, but magnifying the standard images simply makes the image bigger; it does not show more calcifications than were present on the original image nor does it improve image sharpness. These tools simply make whatever was on the original mammogram larger, and if the image was not sharp, they make the nonsharp image larger.

On the other hand, air-gap magnification mammography with a 0.1-mm focal spot actually increases the resolution power of the imaging system by about 1.8 times normal and shows more calcifications than were present on the original image. Air-gap magnification separates closely grouped calcifications into their individual forms, displays faint calcifications not detected at screening, and sharpens the image (see Fig. 1-2). Thus, air-gap magnification mammography is an integral part of calcification analysis and should be obtained on all calcifications requiring further analysis.


Calcifications form in breast ducts (Fig. 3-1), in lobules (Fig. 3-2A), or within breast tumors. Calcifications forming in the interlobular stroma, in periductal locations, or in blood vessels, fat, or skin are usually benign. Recognizing the location is important because calcifications within the skin, muscle, or nipple are almost invariably benign. Skin calcifications are especially important to recognize because they can easily be mistaken for intraparenchymal calcifications, leading to unnecessary biopsy. Skin calcifications are usually tiny, about the size of the skin pore on the mammogram, and often occur in skin folds where skin touches skin (e.g., axilla, inframammary fold, or in between the breasts). They are classically eggshell-type or contain a lucent center.

In general, clustered intraparenchymal calcifications are more suspicious for cancer than scattered calcifications. To be considered a suspicious intraparenchymal cluster, the finding must represent a true cluster and not simply be scattered calcifications superimposing on one another. The cluster must be tightly grouped on two orthogonal views to prove it is not a fake cluster (see Fig. 3-2B). To prove that clustered calcifications are truly grouped together, the radiologist looks for similar-appearing clustered calcifications over the same volume of tissue on orthogonal views. If the cluster is tightly packed on orthogonal views, it is a true cluster and should be assessed further. If the cluster is tightly packed on one view and scattered on the other view, it represents a superimposition of calcifications, is a fake cluster, and can be dismissed.

BI-RADS® Lexicon for Calcifications and Individual Calcification Shapes

The American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS®) lexicon has a good section on description and assessment of calcifications. In the mammography report, radiologists use BI-RADS® terms to describe calcification forms, distribution, location, associated findings, and whether any change has occurred since the previous study. BI-RADS® terms are powerful descriptors that help the clinician understand the seriousness of the finding, such as fine linear branching in cancers. The BI-RADS® terms also help the radiologist classify calcifications into BI-RADS® assessment categories, which prompt patient management (Boxes 3-1 and 3-2). For example, the BI-RADS® term pleomorphic, which is suspicious for cancer, would prompt the radiologist to classify the calcifications into a BI-RADS® category 4, which calls for biopsy to be performed, whereas the term large rodlike, which indicates benign secretory disease, would be classified as a BI-RADS® category 2 and would be dismissed.

BI-RADS® terms are based on calcification morphology. Knowing the underlying anatomic structure in which calcific particles form helps the radiologist to understand why some calcific shapes have specific morphologies and why they suggest benign or malignant disease. An example of how anatomic structures influence calcification shapes are the round calcifications that form in round benign terminal breast acini or lobules. These benign calcifications take on the round shape of the acini in which they form, and hence, are round, regular in shape, densely calcified, and sharply marginated (Fig. 3-3A to C). The BI-RADS® term for these calcifications is punctate; they are usually benign.

The BI-RADS® term amorphous or indistinct describes indeterminate calcifications that are tiny, roundish, flake-shaped particles that are too small and vague to allow further characterization. Both benign and malignant processes produce this type of calcification (Box 3-3). Benign fibrocystic disease and sclerosing adenosis produce blunt duct extension and ductal dilatation that result in indeterminate amorphous or indistinct calcifications (see Fig. 3-3D to F). However, some amorphous or indistinct calcifications can also form in ductal carcinoma in situ (DCIS) (see Fig. 3-3G to J). This overlap between benign- and malignant-appearing calcifications results in “false-positive” biopsies and accounts for up to 75% of benign biopsy results from procedures prompted by calcifications.

Calcifications that develop in DCIS or invasive ductal cancer grow in breast ducts and have classic appearances (Fig. 3-4A and B). The ACR BI-RADS® term for these calcifications is fine linear or fine linear branching (casting) calcifications. These calcifications have linear forms because DCIS grows in branching ducts and the calcifications form within the DCIS, making tiny irregular casts of the duct. These calcifications may look like little broken needles with pointy ends or may have a “dot-dash” appearance with both round and linear shapes. Calcific casts of tumors growing in duct branches form X-, Y– or Z-shaped calcifications. Radiologists describe these classic calcifications as fine linear, fine linear branching, casting, or pleomorphic in the report to reflect their concern for cancer. This is in contradistinction to benign-appearing round, punctate calcifications (see Fig. 3-4C to E).

Another suspicious calcification form described by the ACR BI-RADS® lexicon is pleomorphic or heterogeneous (granular). This term reflects very tiny, irregularly shaped calcific particles that look like bizarre broken glass shards forming inside pockets of necrotic tumors, such as the micropapillary or cribriform forms of DCIS (Fig. 3-5). The individual calcifications are roughly round in shape but have irregular borders, are faint, smaller than 0.5 mm, and vary in size and density. A cluster containing granular calcifications may not exhibit casting or linear forms but should still be considered suspicious even in their absence. Occasionally, granular calcifications form in a duct and look like sand stuffed in a plastic straw. Unfortunately, benign disease occasionally mimics DCIS and also forms granular calcifications (see Fig. 3-5B to G).

DCIS is classified into high-, intermediate-, and low-grade forms. The description of the histologic architecture of DCIS uses words such as comedocarcinoma, which describes the appearance of the comedos of extruded thick tenacious material that resembles a pimple and often calcifies centrally. The terms micropapillary, solid, and cribriform reflect the DCIS architecture in the duct.

It used to be thought that specific suspicious calcification forms suggested specific DCIS histologies, but this is a myth. Although comedo-type DCIS calcifications are often “casting” and micropapillary and cribriform DCIS calcifications are often “granular,” Stomper and Connolly showed that DCIS subtype calcification forms overlap within histologic types. Casting or granular calcifications do not predict a specific DCIS histology, nor do they predict whether cancer is microinvasive or invasive. Casting or granular calcifications can form in DCIS and in microinvasive or invasive ductal cancer. Thus, the radiologist cannot predict if suspicious calcifications are signs of invasive or noninvasive cancers.

Because calcifications can be the only sign of malignancy, is important to analyze all of the individual calcifications in a cluster. Radiologists should not dismiss a calcification cluster simply because it contains a few round benign-appearing calcifications. DCIS may form some benign-appearing round calcifications by spreading into a round lobule, a development called cancerization of the lobule. This results in a few round or amorphous calcifications mixed in with pleomorphic calcifications. Thus, the presence of a few round benign-appearing calcifications within a cluster does not exclude a diagnosis of cancer. The radiologist should decide to biopsy a cluster based on the worst-looking calcifications in the group.

Calcification Group Shape or Distribution within the Breasts

Calcification distributions that may represent cancer in the ACR BI-RADS® lexicon are those described as clustered or grouped, linear, branching (calcifications in a line that may show branching) (Fig. 3-6), and segmental (Fig. 3-7). Cancer forms in diseased ducts within a breast lobe, or the so-called “sick lobe,” as described by Tot and Gere.

Isolated calcification clusters suggest an isolated disease process in a small volume of tissue. This may represent DCIS, invasive cancer, fibrocystic change, papilloma, or sclerosing adenosis. For clusters, one analyzes both the individual calcification forms and the overall cluster shape, which may be a clue to whether the cluster is benign or malignant. Lanyi suggested that the overall cluster shape is especially suspicious if it has a swallowtail, or V, shape, because it suggests cancer in tumor-packed branching ducts. On the other hand, calcifications forming in round clusters may be forming in acini and be benign, especially if the individual calcifications within the cluster are also benign-appearing (see Fig. 3-7E).

The ACR BI-RADS® terms linear branching and segmental describe suspicious findings because they suggest a process within a duct and its branches. The term linear describes calcifications in a line and can represent tumor in a duct or a focal benign process. A segmental distribution is suspicious for cancer because it suggests a process within a branch and its ducts. Segmental calcifications cover slightly less than a quadrant and form in a triangle with its apex pointing at the nipple (see Fig. 3-7F to H).

BI-RADS® terms suggesting benign calcification distributions include regional and diffuse/scattered (see Fig. 3-7I). This pattern suggests innumerable scattered and occasionally clustered calcifications widely dispersed over the breasts and often reflects benign processes, which are also often spread widely throughout both breasts. Calcifications widely distributed in both breasts are usually due to fibrocystic change. Regional calcifications extend over more than one ductal distribution (Box 3-4). Diffuse extensive benign-appearing calcifications in both breasts rarely represent breast cancer. The decision to biopsy calcifications is based on their distribution within the breasts, the worst features of the individual calcification clusters, change over time, the clinical scenario, and common sense.

Benign Calcifications

The specific benign calcifying entities covered in the following subsections require no further workup and should prompt no further action (Box 3-5).

Box 3-5 Typically Benign Calcifications

Artifacts (deodorant, hair, fingerprints)

Skin artifacts: antiperspirant, material in moles

Eggshell-type calcifications, radiolucent centers

Fat necrosis (postbiopsy, post-trauma)

Vascular calcifications (tram-track appearance)

Fibroadenoma (mass with round, coarse peripheral calcifications)

Plasma cell mastitis or secretory disease (needle-like or sausage-shaped calcifications pointing toward the nipple; found in middle-aged women; benign entity, usually asymptomatic)

Milk of calcium (linear on the mediolateral view, smudgy on the craniocaudal view)

Dystrophic calcifications (be alert for such calcifications in women after biopsy for cancer)

Suture calcifications (cat gut, postradiation)

Dec 24, 2015 | Posted by in BREAST IMAGING | Comments Off on Mammographic Analysis of Breast Calcifications
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