Asymmetry on the Craniocaudal View

Presentation and Presenting Images

( ▶ Fig. 67.1, ▶ Fig. 67.2, ▶ Fig. 67.3, ▶ Fig. 67.4, ▶ Fig. 67.5, ▶ Fig. 67.6)

A 65-year-old female with a history of a right mastectomy for intraductal and invasive ductal carcinoma presents for routine screening mammography.

67.2 Key Images

( ▶ Fig. 67.7)

67.2.1 Breast Tissue Density

The breasts are heterogeneously dense, which may obscure small masses.

67.2.2 Imaging Findings

The patient had a right mastectomy. The left breast demonstrates a 1-cm asymmetry (circle in ▶ Fig. 67.7) seen only on the craniocaudal (CC) view. It is located in the posterior depth, 8.5 cm from the nipple. This represents a new finding since the prior mammogram. The two stereotactic clips (T-shaped and rod-shaped) denote the sites of prior benign biopsies.

67.3 BI-RADS Classification and Action

Category 0: Mammography: Incomplete. Need additional imaging evaluation and/or prior mammograms for comparison.

67.4 Diagnostic Images

( ▶ Fig. 67.8, ▶ Fig. 67.9)

67.4.1 Imaging Findings

The finding is much less conspicuous with spot compression and has an appearance most consistent with undercompressed breast tissue ( ▶ Fig. 67.9). The spot-compression view and tomosynthesis confirm that the finding is secondary to overlapping breast tissue.

67.5 BI-RADS Classification and Action

Category 2: Benign

67.6 Differential Diagnosis

Overlapping breast tissue: Undercompression can cause summation artifacts and pseudomasses.
Fat necrosis: This finding is in the immediate vicinity of one of the two stereotactic clips making fat necrosis a reasonable diagnostic consideration. This is unlikely because the finding is more conspicuous than noted on the prior study. Although fat necrosis can have a variety of appearances, it would be expected to become more lucent over time.
Breast cancer: Patients with a prior history of breast cancer are at an increased risk of developing another breast cancer. Cancers, specifically invasive lobular carcinomas, may present as a one-view finding.

67.7 Essential Facts

Although the spot-compression view cleared the finding, the digital breast tomosynthesis (DBT) movie provided additional confirmation that the finding was the result of undercompression and overlapping breast tissue.
Overlapping breast tissue is a common consequence of positioning and of compressing the breast to obtain a two-dimensional mammogram.
Variability in positioning can have a greater effect on mammography than on other imaging modalities and produce summation artifacts seen on only one view.
The most common cause of a one-view finding at screening mammography is overlapping breast tissue.
Breast cancers may present as a subtle one-view finding or may go undetected on the second view.

67.8 Management and Digital Breast Tomosynthesis Principles

Misinterpretation of one-view findings may lead to a missed or delayed cancer diagnosis.
DBT reduces or eliminates the effect of overlapping breast tissue.
DBT reduces the recall rate; however, the interpretation time for tomosynthesis is greater than the interpretation time for conventional mammography. This is the case with any new modality. In time, with use, the interpretation time should decrease.
On the DBT movie, the area of the density was localized to the upper inner quadrant at the 10 to 11 o’clock location. Although it was not done in this case, a mediolateral (ML) tomosynthesis movie with attention to the superior breast could have been performed and would have provided additional evidence regarding the benignity of this finding.

67.9 Further Reading

[1] Giess CS, Frost EP, Birdwell RL. Interpreting one-view mammographic findings: minimizing callbacks while maximizing cancer detection. Radiographics. 2014; 34(4): 928‐940 PubMed