What are microcalcifications?

UPDATED on November 5th, 2022

Microcalcifications are small calcium deposits in the breast that are becoming increasingly common with the progress of mammography technology.

When they are detected, their shape, number, grouping, topography (localization in the breast), size, morphology, and morphology of their grouping are examined.

Calcifications can be intra-galactophore (in the breast milk ducts), vascular (in the vessels of the breast), located in the epithelium bordering the breast milk duct, or in the supporting tissue of the breast.

In mammographic practice, three main situations can be identified: typically benign calcifications, typically malignant calcifications, and intermediate conditions. Of course, the clinical context must be considered when determining malignancy or benignity based on the images. For example, a clinically and ultrasonographically malignant nodule with a few non-concerning calcifications at the edge should not lead to ignoring the other arguments of a suspicious lesion. In contrast, if nothing clinically significant but very concerning calcifications are present, they should prompt further examinations and, if necessary, a biopsy.

The BI-RADS classification of your breast examination will be determined by the presence of microcalcifications and their morphology.`
BI-RADS 2 means typically and with great certainty benign calcifications.
BI-RADS 4 and 5 require a biopsy because they are most probably (for ACR 4) and definitely (for ACR 5) malignant.
BI-RADS 3 represents a situation that is not typically malignant but requires follow-up and rechecking, such as a cluster of calcifications that did not previously exist or an existing cluster that has changed slightly.

We will see later the difficulties and pitfalls of these situations.

Calcifications in systematic mammography:

They are present in 30% of mammograms ! They are the source of the detection for:
- 70% of small invasive cancers less than 5 mm
- 90% of in situ cancers
Later in the article, we will come back to the in situ lesions and explain what their detection on mammography means for a patient.

ACR 2 - almost certain to be benign

► They follow the morphology of an identifiable anatomical structure:
► Macrocalcifications: an adenofibroma, a cyst wall, a secretory ductal ectasia, a plasma cell mastitis, a vessel, a surgical scar.
► Sedimented macro or arciform microcalcifications (often in microcysts).
► Cutaneous microcalcifications.

ACR 5 - almost certain malignant

Highly suspicious abnormality, requiring surgical excision.

► Vermicular, arborescent, branch-like microcalcifications...
► Opacity with microcalcifications within it
► Grouped microcalcifications that have increased in number from one check to the next
► Grouping calcifications follow a galactophoric path or are arranged in a triangle as if following an area of galactophorous ducts.
► The gradation in size and density from the center to the periphery of a cluster of calcifications with a dirty washed-out appearance of the more distal calcifications is a highly suggestive sign of malignancy.

ACR 4 - probably malignant

These are abnormalities considered indeterminate or suspicious and requiring histological verification:

* Numerous regular punctiform microcalcifications and/or grouped in clusters that are neither round nor oval
* Dusty microcalcifications, numerous and clustered
* Irregular, polymorphic microcalcifications, few

ACR 4 means that there is a suspicious abnormality that should be checked. Sometimes it is cancer, but not necessarily. ACR4, therefore automatically implies a biopsy under ultrasound (micro-biopsy). For microcalcifications that are only visible on X-ray, this will be done under X-ray control via a procedure called mammotome (macro-biopsy) or sometimes directly by biopsy-exeresis if the cluster is small enough to be removed entirely by mammotome.
We suspect cancer, but we could be mistaken, or it could be a slow-growing or aggressive form of cancer. The image that prompted us to define it as ACR4 tells us nothing about the aggressiveness of cancer if the biopsied material is indeed cancer!
Because of these uncertainties, this ACR4 classification has been subdivided, with a range of cancer probability assigned to each subdivision.

Click to enlarge

But what about calcifications other than ACR 2 and ACR 5?

This is where things get complicated.
None of the following features:
-round or oval shape of the cluster
- the presence of multiple clusters of identical morphology
- stability over time
► are sufficient to assure with absolute certainty of benignity.

The multifactorial nature of the information to be synthesized makes any strict classification impossible. There are infinite varieties of transitions for each description. The shape, the size, and the number depend on the technique, the information material, and the breast density. Attempts at coding have failed, and we are now faced with a very big problem of dealing with these intermediate images, which are not always known with certainty.
In these situations, the "expert" readers and reviewers only agree in half of the cases.
Frequently, women are subjected to closer "monitoring," more X-ray images, and many consultations. They all attest to the stress and inconvenient nature of these frequent tests, which need their availability and organization in their professional activities, which is constraining. With the increase in anxiety generated by the numerous so-called "awareness" campaigns, with media slogans such as "every minute counts," the wait-and-see attitude that consists of following up and rechecking the sites of microcalcifications (according to what is generally recommended, once every 6 months and then once every year *) is increasingly being abandoned.

Currently, we see in practice that the ACR 3 classification (surveillance) is gradually disappearing in favor of an over-classification "just in case" towards ACR 4.

ACR 4 is now a true catch-all that will determine and justify for the patient a histological confirmation, and so a biopsy, along with the placement of a localization clip, just in case of further surgical intervention.
In fact, due to the increased concern of the doctor, who fears legal action if he does not alert the patient immediately, and the patient, who believes that even the slightest delay could cost her life, the examination is readily upgraded from ACR 3* to ACR 4. Consequently, the number of percutaneous biopsies has increased exponentially.
Simultaneously, the biopsy yield (the number of tumors diagnosed / number of biopsies performed) has declined to approximately 30%. Before less than ten years ago, it exceeded 50%.

* The French referential (page 21) is as follows:
Lesions classified as ACR 3 = No indication for systematic biopsies. However, close monitoring is necessary: monitoring at 6 months for calcifications and at 4 months for masses - In the event of stability during this first follow-up => new close evaluation at 1 year, then at 2 years from the initial examination:
-Stability of the lesion over 2 years enables reclassification as benign, ACR2.
-The lesion is classified as at least ACR4 if there is an increase in size (>10%) or appearance of pejorative morphological characteristics during this follow-up.

Even though mammography has a higher sensitivity for calcifications, these calcifications may be detected for the first time on the initial x-ray. There is a temptation to promptly do a biopsy to provide reassurance, resulting in needless exams, false alarms, and considerable patient stress.

In other words, more and more benign lesions are being biopsied when a simple follow-up and recheck would have ruled out cancer.

Summary of the ACR classification of calcifications.

Positive predictive value (PPV) is the probability that the screened woman is really ill when the screening test is positive. This answers the question, "Doctor, with this abnormality discovered, what is my risk of developing breast cancer?"

The case of carcinoma in situ

This is essentially a mammographic finding. Mammography reveals microcalcifications in 90% of women with DCIS (ductal carcinoma in situ). If not detected, the vast majority of these lesions are not life-threatening. Their prognosis is excellent, with a 10-year survival rate (a parameter widely used by health authorities) of more than 95%. There is a ductal form and a lobular form, rather considered a risk factor for breast cancer.

DCIS is a significant contributor to overdiagnosis. DCIS is treated as "real" cancer in France by surgery and radiotherapy (French referential page 55).

According to trials and studies, increased detection of DCIS has not reduced breast cancer mortality. DCIS accounted for less than 5% of all breast cancers before the screening era, but this has increased to 15-20% in all countries where screening campaigns are in place.

What about MRI?

Because of its low specificity (probability that the screening mammogram remains negative when the screened woman is not ill), MRI, especially in young women, can be positive for calcifications when the patient does not have cancer.

This examination can produce false positives for benign breast abnormalities (various mastopathies) or false negatives despite the presence of carcinoma in situ.

The MRI is inappropriate for microcalcifications.


A course

For those interested, for midwives, doctors, and students, the course given by Dr. Bernard Duperray, former Head of the Imaging Department at Saint Antoine Hospital, Paris: https://cancer-rose.fr/2021/02/24/cours-calcifications-du-sein/

And also: https://cancer-rose.fr/2021/02/24/fausses-microcalcifications/

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Cancer Rose is a French non-profit organization of health care professionals. Cancer Rose performs its activity without advertising, conflict of interest, subsidies. Thank you to support our activity on HelloAsso.