Both benign and malignant breast lesions can be identified on ultrasound.14,15
This benign finding is often seen bilaterally, especially in women in their 30s and younger. FCC can also be seen in post-menopausal women depending on age-related degeneration of the glandular tissue. For women less than 30 with a palpable mass, ultrasound is the diagnostic test of choice. Mammography has decreased sensitivity in women with dense breasts, so ultrasound is commonly ordered on these patients as an adjunct to mammography. Commonly the breast parenchyma (mammary zone) is hyperechoic with prominent ductal anatomy. In a younger patient this may appear as “honeycombing”.16 In older patients, the increased reflexivity may make deeper structures difficult to identify. Of note, fibrocystic change can sometimes have focused hypoechoic areas containing ill-defined margins that sonographically mimic malignancy. Biopsy in this case may be indicated. If a benign result is found, it is essential to establish concordance with ultrasound, mammogram, and physical examination.
Cysts are very commonly seen on ultrasound. Their size and location in the breast are variable, and they are typically round or oval in shape. Simple cysts are well circumscribed, anechoic, demonstrate posterior enhancement, and have thin edge shadows. They are mobile and do not cause any surrounding tissue changes. Simple cysts may be drained if symptomatic; however, intervention is not necessary for these lesions.17 If all criteria for simple cysts are not met, the cyst is considered complex and aspiration or biopsy may be warranted as described below (Figures 5-4 and 5-5).18
Papillomas sometimes present with symptoms including pathologic nipple discharge, which is unilateral, spontaneous, and often bloody. They may be visualized as a mass on mammography, usually as a small solid lesion within a duct near the nipple (although they may also be present more peripherally). The size of papillomas can vary; however, they may be as small as 1 or 2 mm. Papillomas are usually round in shape with a horizontal tumor axis, making them wider than tall, with well-circumscribed margins. Most papillomas are hypoechoic, moderately compressible, and mobile. Surrounding tissues may demonstrate ductal dilation and duct ectasia.16 Core biopsy is usually warranted, although papillomas tend to fragment easily. Surgical excision may be recommended for smaller symptomatic lesions. Surgical excision is recommended for papillomas due to a 5–15% risk of malignancy on pathology from definitive excision (Figure 5-6).19
This is the most common benign solid mass in the breast. Fibroadenomas usually present in 20- to 35-year-old females with a palpable mass. Physical examination characteristics include round or oval shape, rubbery texture, and mobility. Significant growth can be seen while on oral contraceptives or during pregnancy. Fibroadenomas are usually in the 10–30 mm size range and their location is variable.10,16 They have a wider than tall appearance on US and a well-circumscribed margin; however, they can also appear lobulated. Fibroadenomas will appear hypoechoic on ultrasound with posterior enhancement, are not compressible, are easily mobile, have a clear interface with adjacent tissue, and are not associated with surrounding tissue changes. They can sometimes have double edge shadowing posteriorly (Figure 5-7).
Cystosarcoma phyllodes are rare breast tumors that have a sonographic appearance similar to fibroadenomas. They should be in the differential diagnosis of any fibroadenomatoid lesion, particularly in women in their 40s. They usually present with a rapidly enlarging breast mass over several weeks or months. Phyllodes are also usually larger than fibroadenomas at presentation.16 Sonographic characteristics include round or oval shape, horizontal long tumor axis, well-circumscribed margin, abrupt interface with surrounding tissue, hypoechoic pattern which may contain anechoic or cystic components, posterior enhancement, not compressible, and moderate mobility. Surrounding tissue may appear hypervascular, sonographically. Wide local excision is recommended for benign as well as malignant lesions, since both can be locally aggressive. Lymph node evaluation is not indicated for evaluation of metastases, since the metastatic pattern is similar to sarcoma (to the lungs rather than the lymph nodes).
Infections of the breast can affect females of all ages. Mastitis may or may not be associated with systemic signs, and may be localized within the breast or involve the whole breast. It is most commonly associated with staphylococcal infections, and is divided into two categories: lactational and nonlactational mastitis. Lactational mastitis is directly associated with breast feeding and usually occurs within days of instituting breast feeding. Nonlactational can be periareolar or peripherally located. Ultrasound can be very useful in differentiating mastitis from a discrete breast abscess. The ultrasound appearance of mastitis is skin thickening or edema, and edema may be present throughout the breast tissue. The margin of mastitis is indistinct and the boundary is poorly defined. Mastitis is likely to appear hypoechoic on sonography with moderate compressibility.10 Sonography can also identify dilated lymphatics as well as enlarged axillary lymph nodes that are reactive in nature. Ultrasound, however, cannot differentiate mastitis from inflammatory breast cancer. If the breast does not clinically respond to antibiotics, a biopsy should be performed (Figure 5-8).
There are a number of other additional benign breast lesions that can be identified on ultrasound; however, these are much less common than those listed above. These include lactating adenomas in pregnant or lactating women, galactoceles, hamartomas, and breast lipomas (Figures 5-9, 5-10, 5-11, and 5-12).
Intramammary lymph nodes can often be seen within the breast tissue. Enlargement on mammography and ultrasound is considered abnormal. Benign reactive lymphadenopathy is associated with central (hilar) hyperechoic preservation and symmetrical hypoechoic- surrounding cortex. Roundness, loss of hilar hyperechoicity, and eccentric cortical thickening, particularly in the presence of underlying malignancy, are suggestive of malignant involvement of the node.7 If lymphoma is suspected, excisional biopsy is often performed to obtain enough tissue for hematopathology analysis (Figure 5-13).
Suspicious axillary lymph node.
Ductal carcinoma in situ (DCIS) is the most common noninvasive breast cancer. DCIS is usually identified on mammography as clustered, linear, or branching calcifications. Ultrasound is useful in correlation with mammography in DCIS, to identify whether a mammographically occult mass is present. This would allow for ultrasound-guided biopsy as opposed to stereotactic biopsy.20 In addition, if a mass is identified, biopsy may facilitate preoperative upstaging of the lesion. DCIS is treated as a cancer, with lumpectomy, radiation, and endocrine therapy as appropriate (Figure 5-14). Lobular carcinoma in situ is most often an incidental finding with variable sonographic appearance, indicating an increased risk of cancer in both breasts.21
Invasive Ductal Carcinoma
Invasive cancers can present as an imaging abnormality or as a palpable mass in the breast. The presence of any suspicious findings for malignancy warrants a biopsy for tissue diagnosis. Invasive ductal carcinoma is variable is size and location. Lesions usually have an irregular shape, with jagged edges and indistinct margins. They are hypoechoic masses that are taller than wide (with a lateral/anteroposterior ratio of less than 1). There is noted to be posterior shadowing (rather than enhancement) with poor through-transmission. These lesions will be rigid with no compressibility. Most carcinomas will still be moderately mobile on examination and ultrasound. There is also noted to be architectural distortion in the surrounding tissue, disrupting the natural tissue planes (Figure 5-15).10,16
Invasive Lobular Carcinoma
Invasive lobular carcinomas are more difficult to identify on imaging and clinical examination. Lobular carcinomas display a wide spectrum of appearances on mammogram and ultrasound. Sonographically, ILC may appear as an irregular hypoechoic mass with spiculated margins and posterior acoustic shadowing. It can also appear as an ill-defined region of architectural distortion with no discrete mass visualized. Lobular carcinomas can also be difficult to identify on physical examination, as they may present with a “thickening” rather than a discrete mass. Histologically, these cancers have an “indian-file” orientation on histology, with finger-like projections that can make it difficult to obtain clear margins surgically (Figure 5-16).22
As discussed above, the lymph nodes in the axilla should be included in routine ultrasound in the setting of a known malignancy. Lymph node involvement affects medical treatment and surgical planning. To classify a lymph node as morphologically abnormal, the following criteria should be met:
- Enlargement >10 mm in short axis (resulting in a “round” lymph node)
- Loss of hilar hyperechoic center
- Asymmetric focal hypoechoic cortical lobulation
- Uniformly hypoechoic lymph node
If these criteria are met, a biopsy should be performed to rule out metastatic lymph node involvement.23 If lymph node positivity is established preoperatively, then the sentinel lymph node procedure is not necessary at the time of surgery and axillary lymph node dissection is considered. In some instances, knowing that the lymph node is positive preoperatively may change the algorithm for the patient’s cancer care in that neoadjuvant chemotherapy may be recommended prior to surgery.
Features suggestive of reactive lymphadenopathy include nodal matting and surrounding soft tissue edema, with prominent hilar vascularity on Doppler US. Doppler US features suggestive of malignancy include peripheral or capsular vascularity, avascular areas, displacement of vessels, and aberrant course of hilar vessels.10