There is marked variation in the sonographic appearance of normal breast tissue, just as there is in the mammographic patterns. In addition, there is considerable variation in the sonographic appearance of breast pathology. These features result in overlapping of the appearances of normal, benign, and malignant processes and present the examiner with significant challenges. Because of this complexity, most ultrasound lesions are assessed based on a combination of features.16 This section reviews the ultrasound features of some of the more common benign and malignant lesions.
Fibrocystic changes are found in up to 60% of women. These changes begin at the level of the terminal duct and ductal-lobular unit and are felt to be the result of cyclical hormonal influences. As the name suggests, fibrocystic condition reflects a combination of periductal fibrosis and cyst formation. Appearances depend on the ratio of fibrous to cystic elements and on the size of the cysts. The simplest presentation is that of a simple macrocyst (Figure 41-6). If a mass is circumscribed, anechoic, and demonstrates good sound transmission, it is a simple cyst and requires no further evaluation unless aspiration is desired for symptomatic relief.2 It is important to use proper technique when evaluating cysts to make sure that real echoes within the mass are not suppressed by a low gain setting. Simple cysts may be gently lobulated and may have thin avascular septations.
Simple cyst: anechoic, thin circumscribed wall, and enhanced ultrasound transmission.
Simple cysts are straightforward, but cysts may also demonstrate complicated and complex appearances. A complicated cyst is a cyst that meets the criteria for a simple cyst but also contains internal echoes that are not felt to be artifactual (Figure 41-7). Again, proper technique is necessary to make sure that the gain setting is not so high as to suggest internal echoes when none exist.14 Complicated cysts are managed based on the context. If it is an isolated finding or a finding that corresponds to a new palpable mass, aspiration would be undertaken to confirm its cystic nature and resolve the palpable finding. If it is seen in the presence of multiple other simple and/or complicated cysts, further evaluation may not be required. In this setting it is important to make sure that all of the cysts are circumscribed, that none contain internal blood flow and that there are no malignant features. Following multiple small complicated cysts with ultrasound is technically challenging and usually unnecessary.
Complicated cyst: low-level internal echoes, thin circumscribed wall, and enhanced ultrasound transmission.
Complex cysts in the breast are like complex cysts in the ovary—they contain cystic and solid elements (Figure 41-8). Generally, the concern is over a focal abnormality of the wall such as eccentric thickening (especially if convex inward) or nodularity. They may or may not have internal echoes, but usually have some degree of sound transmission. The concern here is over the possibility of an intracystic neoplasm, such as a papilloma or malignancy.17 In general, complicated cysts should not undergo aspiration as removal of the fluid component may make it difficult to identify any residual solid component. Complex cysts are usually biopsied, either with image-directed core or vacuum-assisted biopsy, or with excision.18 If image-directed biopsy is performed, a marking clip should be deposited in case pathology is positive and no sonographic residual remains.
Complex cyst with solid and cystic components.
Sonographic features are more variable for microcysts19 and clusters of cysts, especially when there is associated fibrosis (Figure 41-9). Incidental clusters of simple-appearing micro- and macrocysts can often be followed, but if there is any question of an associated soft tissue mass, biopsy should be considered, as the appearance of early invasive and intraductal malignancy can overlap with the appearance of some clustered microcysts.
The first step with solid masses is characterization based on margins, echogenicity, sound transmission, and relationship to adjacent structures.
Benign features for solid masses include2,16:
Oval, round, or gently (macro) lobulated margins (Figure 41-10)
Circumscribed (smooth) margins (Figure 41-10)
Continuous thin capsule surrounding the nodule (Figure 41-10)
Thin surrounding halo
Long axis parallel to the skin ("wider than tall") (Figure 41-10)
Adjacent structures displaced rather than distorted
Reniform shape with echogenic hilum (lymph node)
Malignant features for solid masses include2,16:
Irregular, angular, indistinct, microlobulated, or spiculated margins (Figure 41-11)
Long axis non-parallel to the skin ("taller than wide") (Figure 41-12)
Associated microcalcifications (Figure 41-13)
Extension of the lesion into adjacent ducts (Figure 41-14)
Adjacent structures distorted
Posterior acoustical shadowing (Figure 41-11)
Fibroadenoma with parallel orientation and thin, continuous capsule.
Invasive ductal carcinoma with spiculation and posterior acoustic shadowing.
Invasive ductal carcinoma with non-parallel orientation and angular margins.
Ductal carcinoma in situ with specular reflectors indicating microcalcifications.
Invasive ductal carcinoma with (A) duct extension and (B) branch pattern.
A mass with any malignant feature should be regarded as suspicious and biopsy should be performed. An incidental mass with no malignant features, smooth or gently lobulated margins, and thin continuous capsule has less than a 2% risk of malignancy and can be followed.16 Most other solid masses are biopsied unless stability has been previously demonstrated.
Although there are particular features that may be associated with different benign solid masses (eg, papillomas, fibroadenomas, phyllodes tumors, etc), it is generally not necessary to predict a precise etiology as most will undergo biopsy. There are also different features that may be seen in different forms of malignancy, but, again, since biopsy will be performed, general predictions regarding cell type are usually not necessary.
Skin changes may be seen in a variety of inflammatory and infiltrative conditions and may consist of thickening, edema, and hypervascularity. The correct diagnosis is often made based on the clinical setting and other mammographic and sonographic findings. If there are inflammatory findings that do not resolve with appropriate antibiotic therapy, the patient should be referred for punch biopsy of the skin to exclude inflammatory breast cancer.
Some degree of duct dilatation is frequently seen in the subareolar regions, and internal echoes are frequently seen within these ducts secondary to proteinaceous material or debris. Findings that may indicate the need for additional evaluation include isolated ductal dilatation, intraductal nodules (Figure 41-15), or Doppler flow associated with any echogenic material within a distended duct.
Intraductal papilloma shows a mass within the duct and fluid distending the duct.
There are several sonographic features that may suggest intracapsular or extracapsular rupture of silicone implants. Extracapsular rupture may be manifest as areas of dense irregular echogenicity with posterior shadowing and loss of normal tissue planes. This appearance is referred to as the "snowstorm" pattern. Intracapsular rupture may be seen as layers of implant shell collapsed into the intact collection of intracapsular silicone ("linguine" or "step ladder" signs). Implant characterization can be very complex as there are many different kinds of implants consisting of multiple lumens in various configurations. If there is any concern over implant integrity that cannot be resolved based on ultrasound or mammographic features, breast MRI should be considered.