MAMMOGRAPHY INTERPRETATION Before Reading Mammogram
Step 2. Targeted Search: Anatomical Structures If there was no mass on the initial study and the overall mammo-
Normal asymmetries should have no suspicious calcifications, spiculations, or palpable masses, are stable when compared with older studies, and are composed of fibroglandular tissue.
An asymmetry may be abnormal or indicate cancer if it is pal- pable, has suspicious calcifications or spiculations, is new, or is a mass and not an asymmetry at all; if the patient has any of these findings with an asymmetry they should undergo a workup with ultrasound or biopsy.
The white parts of mammograms can hide masses. Radiologists can see masses if they are whiter than the surrounding tissue or if there is a round or spiculated mass edge projected against dark fat. If the radiologist sees a mass on one projection, the radiolo- gist looks for the mass on the orthogonal view. To do this, the radiologist measures the distance from the nipple to the mass and searches the orthogonal view for the mass at this distance
(see Fig. 2.16). If the finding is seen on two views, it is considered a mass or focal asymmetry. If the “mass” is seen on only one view, it is called an asymmetry or a density and represents either a summation artifact (Fig. 2.23) or a mass that is obscured on the second view (Fig. 2.24). The decision to recall this type of finding and prompt a workup is based on the radiologist’s experience and the degree of suspicion of the one-view finding.
Step 2. Targeted Search: Anatomical Structures
A
New MLO
Old MLO
New CC
B
C
FIG. 2.22 Normal asymmetry. (A and B) Mediolateral (MLO) view (A) shows an asymmetry in the upper left breast, which is not as apparent on the craniocaudal (CC) view (B), representing normal overlapping tissue. (C) An older MLO mammogram shows that the asymmetry is stable.
CC MLO
A B
FIG. 2.23 Asymmetry on one view caused by a summation artifact. (A) On the craniocaudal (CC) view an asym- metric density (arrowheads) is seen in the outer left breast. (B) Review of the mediolateral oblique (MLO) view shows no mass of the same shape or density at the same distance from the nipple (double arrows), suggesting a confluence of shadows. In addition, the asymmetry has no spiculations or calcifications, was not associated with a palpable finding, and did not appear to be a mass. Workup showed that the density represented a summation artifact.
The radiologist sees if the nipple is everted and reviews the complex structures of ducts and vessels in the retroareolar region. The nipple should be seen in profile on at least one mam- mographic view. If the nipple is not in profile on at least one view, it may overlie the retroareolar region and obscure a mass, or it might be retracted by cancer. If the nipple is not seen in profile on any view, the mammogram should be repeated with the nip- ple in profile. If the nipple is truly inverted on the mammogram, the radiologist should check the breast history form to see if it was inverted at birth (normal variant) or if the nipple inversion is new. New nipple inversion is of concern for a retroareolar cancer and prompts a workup.
Normal breast skin is approximately 2-mm to 3-mm thick on the mammogram, and normal subcutaneous fat is dark. The skin should be smooth all around the breast and not pulled in (Fig.
2.26). Skin thickening greater than 2 mm to 3 mm that is asym- metric to the contralateral side is abnormal and is especially wor- risome if the subcutaneous tissue has become gray and the thin tethering lymphatics and ligaments become thick and trabecu- lated. This is worrisome for breast edema. Generally, skin thicken- ing from cancer should be investigated.
The axilla normally contains lymph nodes, which are smooth oval-shaped or kidney bean–shaped masses containing fatty hila on the mammogram (Fig. 2.27A). Lymph nodes that grow larger become dense, round, and lose their fatty hila; they represent lymphadenopathy and are abnormal (Fig. 2.27B).
Axillary breast tissue is a normal variant and consists of breast tissue in the axilla (Fig. 2.28). It develops along the normal nipple line that extends (in animals) from the axilla along the chest to the abdomen. Axillary breast tissue can be, but is rarely, attached to an extra nipple. Spiculated masses in the axilla can mimic nor- mal lymph nodes or axillary breast tissue. Any masses in the axilla should be scrutinized carefully to make sure they are normal lymph nodes or axillary tissue and not cancer (Fig. 2.29).
B A
CC MLO
FIG. 2.24 Asymmetry on one view caused by cancer. (A) More breast tissue is seen in the medial aspect of the right breast on the craniocaudal (CC) view (arrowheads) than in the medial aspect of the left breast. Closer exami- nation shows the density to have a slightly round shape and possible spiculations, unlike the asymmetric density seen in Fig. 2.9. (B) The abnormal density is not identified at the same distance from the nipple as in A (double arrows) on the mediolateral oblique (MLO) view. Follow-up examination confirmed the density to be a true mass and invasive ductal cancer.
FIG. 2.25 Use of the surrounding architecture to detect masses. A craniocaudal spot magnification view shows an equal-density spiculated mass (radial scar at biopsy) producing subtle distortion of the tissue with straightening of Cooper’s ligaments.
A B
FIG. 2.27 Normal axillary and abnormal lymph nodes. (A) A magnified mediolateral oblique view shows multiple normal lymph nodes that have kidney bean shapes with the fatty hilum well visualized (arrows) suggesting they are “normal.” The large fatty hilum with thin cortex causes the lymph node to have a C shape. (B) Abnormal axil- lary lymph node without a fatty hilum (arrow), characteristic of lymphadenopathy, and representing lymphoma.
If the axilla had not been reviewed, this finding would have been missed.