Diagnostic Mammography

1

What are the indications for a diagnostic mammogram?

Some indications for a diagnostic mammogram include a history of breast cancer, breast lump, nipple discharge, focal breast pain, breast implants, history of breast biopsy, history of an abnormal mammogram, and follow-up for a previously evaluated mammographic finding (BI-RADS category 3 lesion).

2

What views are performed for diagnostic mammography? How are patients who have undergone diagnostic mammography informed of results?

Routine views are performed with additional views as needed. Routine views include bilateral craniocaudal (CC) and mediolateral oblique (MLO) views. Additional views may include spot compression views, magnification views, exaggerated views, and rolled views. Ultrasonography (US) may also be performed if indicated. US evaluation may be performed to further evaluate a mammographic finding, such as a mass, or may be performed to further evaluate clinical symptoms, most commonly a clinically palpable breast mass. The imaging evaluation is completed while the patient is present at the imaging center, and the patient is informed of the results before he or she leaves. At our institution, the physician discusses the results with the patient.

3

What is BI-RADS?

The Breast Imaging Reporting and Data System (BI-RADS) lexicon was developed by the American College of Radiology (ACR) to provide a clear, concise way to report mammographic results. A BI-RADS category is reported at the end of every mammogram report and summarizes the findings of the mammogram ( Table 9-1 ).

4

What types of mammographic changes may be seen after breast conservation?

Surgical therapy and radiation therapy often result in tissue distortion and edema. Other findings include skin thickening and trabecular thickening. The first mammogram after completion of therapy serves as a baseline study for the patient. Post-therapy changes, such as the degree of skin thickening and distortion, should remain stable or improve over time. If the post-treatment findings worsen, then there should be concern for recurrent disease and further evaluation is needed.

5

Does mammography have high sensitivity in detecting recurrent breast cancer after breast conservation?

The sensitivity of mammography in detecting recurrent tumor is limited by the post-therapy changes present on the mammogram: edema, distortion, and trabecular thickening. Overall, studies suggest that mammography does not detect tumor recurrence about one third of the time. Recurrence presenting as calcifications is easier to detect than that presenting as a mass after breast conservation therapy. Physical examination also plays an important complementary role in evaluating patients after breast conservation. There is new literature suggesting that breast magnetic resonance imaging (MRI) may detect additional cancers.

6

What is the incidence of recurrent breast cancer in a patient after breast conservation?

Recent literature suggests that recurrence rates are fairly low after breast conservation therapy, less than 1% per year.

7

True or false: In patients who develop recurrence after breast conservation, survival rates are about the same as for patients who had a mastectomy as the initial treatment.

True. Recurrence after breast conservation does not seem to affect the overall survival rate for patients with breast cancer. Survival depends on the size of the recurrence, however.

8

What are some contraindications to breast conservation?

• Multicentric cancer (i.e., the presence of breast cancer in different quadrants of the breast) is a contraindication. If there is multifocal tumor, however (i.e., more than one focus of cancer localized to the same quadrant of the breast), breast conservation therapy is feasible.

• Size of the cancer relative to the breast size is a relative contraindication. Some clinicians use 5 cm as a cutoff; however, others use a relative measurement as a size cutoff. A 6-cm cancer in a large breast may result in acceptable cosmesis, whereas in a small breast, it would result in unacceptable cosmetic results.

• First-trimester or second-trimester pregnancy.

• History of prior radiation therapy to the chest or mediastinum.

• Active collagen vascular disease.

9

In a patient who is planning to have breast conservation, when is it necessary to obtain a postbiopsy mammogram shortly after a successful excisional biopsy?

If the malignancy was associated with calcifications on the mammogram, a postbiopsy mammogram should be obtained to ensure that all the suspicious microcalcifications have been removed. If there are residual calcifications, the likelihood that there is residual disease is quite high. The inverse is not true. If there are no residual calcifications, this does not indicate that there is no residual disease. There may be portions of the cancer that are not calcified. The decision to re-excise is also based on histopathologic margin status.

For breast cancers that manifest as a mass on the mammogram, a postbiopsy mammogram is not needed. The decision to re-excise should be based on the histopathologic margins. Due to the postbiopsy changes in the surgical bed, it would be difficult to differentiate between postbiopsy changes and residual tumor.

10

True or false: In a patient with a history of breast cancer, it is beneficial to get a mammogram more frequently than once a year.

False. No studies have shown a benefit of an increased frequency of screening. Annual mammography is recommended even in women who have a history of breast cancer.

11

What is a 6-month follow-up? How long is the follow-up performed for BI-RADS category 3 lesions?

Six-month follow-up is performed for BI-RADS category 3 lesions (after an appropriate imaging workup). The follow-up is performed for a total of 2 to 3 years at 6-month intervals. For lesions that fit the “probably benign” criteria, less than 2% of the lesions should be malignant. That is, greater than 98% of the lesions should be benign.

12

How is the mastectomy bed evaluated?

We do not recommend routine imaging evaluation of the mastectomy bed. No studies have shown the benefit of routine imaging evaluation of the surgical bed. Instead, clinical evaluation is recommended. If there is a palpable area of concern on the physical examination, US should be performed as the next step of evaluation.

13

What types of surgical reconstruction are available after a mastectomy?

There are various types of tissue flaps, such as transverse rectus abdominis musculocutaneous flaps and latissimus dorsi flaps. Alternatively, silicone or saline implants may be used for reconstruction, or a combination of both.

14

True or false: After a benign breast biopsy, significant residual changes are usually visible on a mammogram.

False. After a benign breast biopsy, the breast tissue usually heals with few residual changes. Infrequently, distortion and postbiopsy changes may persist.