Breast Imaging. Beverly Hashimoto

       Figure 1–2. (A). Right MLO digital mammogram. (B). Left MLO digital mammogram. (C). Right CC digital mammogram. (D). Left CC digital mammogram. (E). Right MLO spot magnification mammogram. (F). Right CC spot magnification mammogram. (G). Right MLO spot magnification mammogram. (A–G). There is a palpable right breast mass that is labeled with a radiopaque dot at the 3:00 location near the nipple. The mass is not well delineated on either the screening or the spot magnification views (E,F). In the right upper outer quadrant in the middle third of the breast (square), there is an irregular mass that is confirmed on the spot magnification view (G). (H). Right antiradial breast sonogram: The palpable mass corresponds to a well-defined oval hypoechoic mass. On this view, the mass appears probably benign. (I). Right antiradial breast sonogram: This is the same mass as Figure 1–2H, but in a slightly different position. Subtle irregularity of the margin (arrow) is present. These features change the assessment so that the lesion is suspicious. This mass is infiltrating mucinous carcinoma. (J). Right antiradial breast sonogram: This hypoechoic irregular mass corresponds to the irregular mammographic mass (G). This mass is infiltrating ductal carcinoma.

      Finally, radial scars also produce irregular masses. The mammographic characteristics of radial scars include: (1) change in appearance from one mammographic projection to another; (2) no dense central mass; (3) the radiating lines are long and thin; (4) the radiating structures are commonly dominated by radiolucent linear lines; (5) no skin thickening; (6) very little palpable abnormality. Although radial scars may be differentiated from malignancy, radial scars are commonly associated with malignant neoplasms and, therefore, should be excised.

      Asymmetric Densities

      Analysis of an asymmetric density should start with a close evaluation of the entire mammographic examination. It is important to initially define if the asymmetric density diffusely involves a large area of the breast or a small area (see Section 6). If the density is diffuse, then the skin should be carefully examined. If the density is only due to increased fibroglandular tissue, then a physiologic or pharmacologic etiology may be responsible. Heterogeneous or extremely dense parenchymal composition is more common in younger premeno-pausal women, but is also common in older women, especially those with fibrocystic changes. Medications such as estrogen replacement therapy sometimes increase the overall mammographic parenchymal density.

      If skin thickening is present then the etiologies include axillary lymphatic obstruction, lymphatic spread of breast cancer, inflammation, and systemic fluid overload. Axillary lymphatic drainage may be blocked by ipsilateral breast cancer metastases or hematologic malignancies (e.g., lymphomas). Lymphatic spread of breast cancer to the contralateral breast will block lymphatic channels and produce lymphedema. Inflammation and abscess will thicken the skin and produce increased density, particularly around the areola. In this situation, the axillary portion of the breast is relatively spared. Finally, any condition that produces systemic fluid overload such as heart failure or renal failure will produce breast lymphedema.

      If the asymmetric density involves a small area, then one should carefully examine the area to determine if the density represents a mass, normal asymmetric fibroglandular tissue, or overlap of normal parenchymal tissue. A focal asymmetric density is a density that cannot be reliably identified on more than one view. If the density is only visible on the craniocaudal (CC)view, a 90 degree mediolateral (ML) may demonstrate the mass better than the mediolateral oblique (MLO) view. Spot compression of a density may clarify the shape of the mass, but sometimes malignancies such as lobular carcinoma may compress and blend into the normal breast parenchymal background. For small or less-dense lesions, consider using rolled or oblique views to confirm the presence of the mass (Fig. 1–3). Normal fibroglandular tissue will blend into the adjacent tissue with oblique views. The tissue will have the same internal curvilinear pattern as the rest of the breast. Furthermore, the tissue will not exhibit any architectural distortion. If one cannot distinguish between a mass and normal fibroglandular tissue, then sonography may be useful. However, to adequately perform this differentiation, one must have high resolution and frequency, be familiar with the normal sonographic appearance of breast parenchyma, and be comfortable with cross correlating mammography with sonography (see Section 2). If the woman is high risk for malignancy and high-frequency sonography is negative or unavailable, then magnetic resonance is a reasonable method to clarify the etiology of a worrisome asymmetric density.

      Calcifications

      There are a wide variety of breast calcifications (see Section 5). Analysis of calcifications should start with excluding calcifications that are characteristic for benign lesions. If the calcification does not fit in these obviously benign categories, then the shape of the calcification should be analyzed and placed into patterns that can be related to American College of Radiology BI-RADS assessment categories.

      Calcifications or densities simulating calcifications that may be excluded from further workup include technical artifacts, substances on the skin (e.g., lotions, deodorants), and calcifications that are pathognomonic for benign entities. Processor artifacts and dirty screens may produce tiny dots or irregularities that are confused for calcifications. These artifacts are generally whiter than calcifications and have unusual shapes. Constant evaluation of processing is critical to avoid these problems. Materials on the skin may also initially appear as calcifications. However, these densities are unusual in configuration and are commonly located in the axilla. Thorough cleansing of the skin prior to reevaluation generally removes these particles. Educating patients to avoid using these materials prior to mammography will also reduce encountering this problem. Certain calcifications are pathognomonic for benign entities. These include oil cyst, dermal, vascular, secretory, and milk of calcium calcifications (Figs. 1–3B,D,G). By reviewing these characteristic calcifications in texts or teaching files, one can confidently identify these benign calcifications.