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CHAPTER SEVEN

Abnormal Mammograms: Calcifications and Densities

OCCASIONALLY, A WOMAN’S SCREENING MAMMOGRAM will show a change from a prior view, despite her being asymptomatic. With these women, additional evaluation is required; further diagnostic evaluation will indicate whether the variations can be safely observed and the patient returned to either a six-month or one-year follow-up.

However, in about 10 percent of cases the difference is of sufficient concern that a biopsy is necessary to make an accurate diagnosis. Two possible changes may have occurred. The most common is the development of new calcifications within the breast; the other is newly revealed areas of increased density.

CALCIFICATIONS

Calcifications are simply deposits of calcium that show up as white dots on a mammogram. Normally, the calcium that circulates in the bloodstream will end up in the bones, but it can be deposited in the breast in response to both benign and malignant changes. The mammographer can readily visualize these deposits. It’s the pattern of crystals that is so important to the radiologist in determining whether they are associated with a small evolving cancer or are of no consequence and can be ignored.

The vast majority of calcifications are not indicative of a problem. For the most part, benign calcifications are smooth, round, and scattered throughout the breast. Malignant calcifications, on the other hand, typically concentrate in one spot. They are also more likely to be irregular in shape and small in size.

In most cases, it is relatively easy for the mammographer to distinguish between benign and malignant calcifications. Calcifications that appear benign can be ignored. With some patients the pattern is considered to be probably benign, but a six-month follow-up is recommended.

When a pattern is suspicious, a core needle biopsy is recommended as the next step (see “Next Step: Options for Biopsy” on page 47).

DENSITIES

The second common change on the screening mammogram, usually prompting a biopsy, is a new density in the breast. A density is basically an accumulation of tissue that produces a distortion that stands out from the surrounding breast tissue.

In some cases, this change forms a starburst (spiculated) shape that is easy for even the inexperienced observer to visualize. More commonly, the pattern is subtle and can only be observed when comparing the present mammographic images with those from the previous year. For this reason, most mammographers insist on having prior mammograms for comparison.

When the radiologist detects a subtle distortion or density on the screening mammogram, the patient will be called back for additional views, along with a diagnostic ultrasound.

The density may or may not contain calcifications. If it does, it’s usually easier for the radiologist to decide on the need for a biopsy. In certain lucky patients, additional views will prove that the density is simply caused by overlapping breast tissue and the patient can return to yearly screening. When findings are labeled as “probably benign,” a six-month follow-up mammogram is recommended.

NEXT STEP: OPTIONS FOR BIOPSY

In the “old days,” when the calcifications or density were judged to be suspicious, the surgeon would simply remove the area of concern. Now, thanks to improvements in imaging techniques, an open surgical biopsy is rarely performed.

Instead, the modern approach to diagnosis is with a core needle biopsy, which takes a sample of breast tissue that is about the size of the lead in a pencil or larger. This sample not only allows for a more accurate diagnosis, but if the spot proves to be a cancer, the core biopsy provides additional information on how the cancer might respond to various treatment options (see chapter twenty-two).

Three types of core needle biopsies are used to make a more accurate diagnosis: ultrasound-guided core needle biopsies, stereotactic core needle biopsies, and MRI-guided biopsies. (For a detailed description of each, see the boxes on pages 48–49.)

When the spot on the mammogram is also seen on an ultrasound, ultrasound-guided core needle biopsy is the procedure of choice because it is quick and easy for the patient. However, calcifications are typically not seen on the ultrasound and an alternative approach, a stereotactic core biopsy or, in select cases, an MRI-guided biopsy, is required, when the area of concern is seen only on the MRI.

If the biopsy proves to be benign, the patient returns to yearly mammographic screening. If the biopsy shows a high-risk change or a cancer, the patient should be referred to a breast surgeon (see Appendix III).

With some women the findings on the biopsy do not match those on the mammogram—for example, the pattern on the mammogram was suspicious, but the biopsy comes back as normal breast tissue. This inconsistency is referred to as a discordant biopsy. In those situations, a second biopsy is recommended, or the patient is referred to a breast surgeon for consideration for an open biopsy.

ULTRASOUND-GUIDED CORE NEEDLE BIOPSY

In the ultrasound-guided biopsy procedure the patient lies comfortably on her back (with a pillow under her head). The radiologist uses the ultrasound to locate the areas of concern. Local anesthesia is injected into the breast and a small incision is made in the skin. Using the ultrasound as a guide, a core needle biopsy device is directed to the area of concern. The device takes several tissue samples. After completion of tissue sampling, a small titanium clip is placed to identify the spot where the sample was taken. A simple dressing is then placed over the skin incision.

The procedure takes fewer than twenty minutes and is remarkably well tolerated by most patients.

STEREOTACTIC CORE NEEDLE BIOPSY

A stereotactic biopsy is performed when the spot on the mammogram cannot be visualized on the ultrasound. In this procedure the patient lies facedown on the biopsy table. The breast is then positioned so that it hangs through a hole in the table. Below the table is a mammogram machine mounted on a swivel, which allows the technologist to take digital images from the left and right side of the breast at 15-degree angles from the center.

The information from the two images is fed into a computer, which calculates the exact position for optimal placement of the needle tip. Local anesthesia is then injected and a small incision is made in the skin. The needle is advanced into the breast tissue. The computer directs the needle to the correct position for taking an accurate core tissue sample.

After a few samples are taken, the needle is repositioned to take additional samples. As with the ultrasound biopsy, a small titanium clip is placed to mark the location, the needle is removed, and a dressing is applied.

This procedure takes thirty to sixty minutes to perform and is generally well tolerated. In unusual cases it is not possible to do a stereotactic biopsy. With some women, the spot is not in a location that can be accessed on stereotactic imaging. In other cases, the patient may not be able to tolerate lying facedown on a hard table. In these rare cases, an open surgical biopsy is typically performed to make the diagnosis.

MRI-GUIDED BIOPSY

We now commonly perform screening MRIs in women who are considered to be at high risk for malignancies (see Appendix I) but have no breast symptoms and have a normal clinical exam. When the MRI shows a suspicious finding, an ultrasound is recommended, and sometimes special mammographic views are as well. If the area of concern cannot be visualized in either study, the biopsy is done with MRI guidance.

MRI biopsy is done with the patient lying facedown on a mobile table with her arms stretched forward. After proper positioning, the patient is slid into the MRI tube. An MRI study is performed and the area of concern is identified. The patient then slides back out of the machine for needle positioning.

The breast is then gently compressed in a grid. Using targeting software, the radiologist pinpoints the position of the tumor in relation to its location on the grid. The radiologist makes the proper adjustment for needle position and from there on the procedure is similar to that for a stereotactic biopsy.

WHAT I’D TELL MY DAUGHTER

• Most abnormal mammograms prove not to be cancer.

• Needle biopsy is the procedure of choice to evaluate an area of concern on the mammogram or ultrasound.

• Open surgical biopsy to make the diagnosis of an area of concern on the mammogram is rarely indicated.