You are in: eMedicine Specialties > Radiology > BREAST Breast Cancer, UltrasonographyArticle Last Updated: Jan 27, 2005AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Steven Perlmutter, MD, FACR, Clinical Associate Professor, Radiology Residency Program Director, Radiology Medical Director, Department of Radiology, University Hospital at Stony Brook Steven Perlmutter is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of Program Directors in Radiology, Association of University Radiologists, Medical Society of the State of New York, Radiological Society of North America, Society of Breast Imaging, Society of Nuclear Medicine, and Society of Uroradiology Coauthor(s): Ben Y Young, MD, Clinical Assistant Instructor, Staff Physician, Department of Radiology, Stony Brook University Hospital; Joseph P DiPietro, MD, Staff Physician, Department of Medicine, Salem Hospital; Paul R Fisher, MD, Clinical Associate Professor of Radiology and Surgery, State University of New York-Stony Brook School of Medicine; Chief, Breast Imaging Section, Department of Radiology, Stony Brook University Hospital; Ajay Malhotra, MD, Clinical Assistant Instructor, Consulting Staff, Department of Internal Medicine, Stony Brook University Hospital; Sheri L Ford, MD, Assistant Professor of Clinical Radiology, State University of New York-Stony Brook School of Medicine; Consulting Staff, Department of Radiology, Section of Breast Imaging, Stony Brook University Hospital; Barbara Larson, RDMS, RDCS, BSRT(R)(M), Staff Sonographer, Section of Breast Imaging, Carol M Baldwin Breast Care Center, Stony Brook University Hospital Editors: John M Lewin, MD, Associate Clinical Professor, Department of Preventative Medicine and Biometrics, Director of Teleradiology, Co-director of Breast Imaging Section, Director of Breast Imaging Research, Department of Radiology, University of Colorado Health Sciences Center; Consulting Radiologist, Diversified Radiology of Colorado; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Edward Azavedo, MD, PhD, Director of Clinical Breast Imaging Services, Associate Professor, Department of Radiology, Karolinska University Hospital, Sweden; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Lawrence M Davis, MD, Assistant Professor of Diagnostic Imaging (Clinical), Department of Diagnostic Imaging, Brown Medical School Author and Editor Disclosure Synonyms and related keywords: breast ultrasound, breast US, breast sonography, mammography, breast cancer screening, breast imaging, breast cancer detection, BI-RADS, American College of Radiology Imaging Network, ACRIN INTRODUCTIONSection 2 of 10
  Mammography is a well-defined and widely accepted technique to evaluate clinically suspected breast lesions and to screen for breast cancer. The widespread application of breast physical examination and mammography has decreased breast cancer mortality rates. Ultrasonography (US) also has been playing an increasingly important role in the evaluation of breast disease. US has also been playing an increasingly important role in the evaluation of breast disease. US is useful in the evaluation of palpable masses that are mammographically occult, in the evaluation of clinically suspected breast lesions in women younger than thirty years of age, and to further evaluate many abnormalities demonstrated on mammograms. Some breast imagers believe that US is the primary modality for the evaluation of palpable masses in women thirty years of age and older and that mammography plays an adjunctive technique. US is also useful in the guidance of biopsies and therapeutic procedures, and more recently research is underway to evaluate its role in cancer screening. Originally, US was primarily used as a relatively inexpensive and effective method to differentiation cystic from solid breast masses. However, it is now well established that US also provides valuable information about the nature and extent solid masses and other breast lesions. Furthermore, US does not expose a patient to ionizing radiation, which is particularly important for pregnant or young patients. It is believed that their breasts are more sensitive to radiation, resulting in a slight increase in the small risk of acquiring radiation-induced neoplasm. Furthermore, young women's breasts tend to appear dense on mammograms, reducing the diagnostic sensitivity of mammography in this group. Another indication for breast US is the evaluation of breast abscesses, which is better done with US than mammography. The role of US in the screening of specific groups of patients, such as those with mammographically dense breasts and those at high risk for breast carcinoma, being investigated. The role of breast MRI is also expanding and under study. In many cases, US provides an efficient and effective way to guide interventional procedures. For excellent patient education resources, visit eMedicine's Imaging Center and Cancer and Tumors Center. Also, see eMedicine's patient education articles Mammogram, Breast Cancer, and Breast Lumps and Pain. ROLE OF SCREENING USSection 3 of 10
Although mammography is an effective screening tool, data suggests that it is often less sensitive in detecting cancer in mammographically dense breast tissue. Kolb et al and Buchberger et al found that careful US may be useful in detecting occult breast cancer in dense breasts. US is generally acknowledged to be a highly operator dependent modality that requires a skilled practitioner, high-quality examinations, and state-of-the-art equipment. In view of the results of these studies, a prospective multicenter study is clearly needed to examine the role of US in breast cancer screening. To meet this need, a large multicenter study supported by the Avon Foundation and the National Institutes of Health was created through the American College of Radiology Imaging Network (ACRIN). In this project, a protocol to assess the efficacy of screening breast US is being implemented in 14 imaging centers to better define the role of US in breast cancer screening. (More information is available on the ACRIN Web site.) The results are anticipated to better define the appropriate role of screening US. Currently, it is recommended that screening breast US be reserved for special situations, such as imaging in highly anxious patients who request it and in women with a history of mammographically occult carcinoma. As of January 2004, screening US of the breast is not generally recommended in high-risk women with dense breasts. Although some of research projects have shown reasonable results from US breast screening, a number of serious issues remain before the practice is recommended for general application. These include interobserver variability, intraobserver variability, unknown sensitivity, and low specificity (leading to numerous biopsy evaluations of benign lesions). Additional studies may be needed before widespread, routine US screening of mammographically dense breasts is recommended. BREAST IMAGING REPORTING AND DATA SYSTEMSection 4 of 10
As mentioned above, US is highly operator dependent. Therefore, its efficacy depends on obtaining studies that are of high technical quality, on their correct interpretation, and on the clear reporting of results. Baker et al and Rahbar et al demonstrated that observer variability varies considerably in the description and assessment of solid masses demonstrated on sonograms. More uniform and more clearly understandable examination reports are needed to improve patient care and also facilitate research in the use of breast US. In 2001 Mendelsohn et al published the results of their initial work to create a standardized breast US lexicon. In 2003, the American College of Radiology (ACR) published the Breast Imaging Reporting and Data System (BI-RADS) Atlas. This document is an extended version of the Third Edition of the BI-RADS lexicon used in mammography. The BI-RADS Atlas includes new sections on breast US (ACR BI-RADS–US) and MRI (ACR BI-RADS–MRI). ACR BI-RADS–US may help standardize terms used for characterizing and reporting lesions, facilitating patient care and the study lesion characterization and possible screening applications. ACR BI-RADS–US provides terms to describe the following features or findings on breast US examinations: shape, orientation, margin, boundary, echo pattern, posterior acoustic features, and surrounding tissue for masses; breast calcifications (which are poorly characterized by US); special cases, such complicated cysts and intramammary lymph nodes; vascularity; and assessment categories. ACR BI-RADS–US describes 7 assessment categories. One category is for lesions that are incompletely characterized and for which further imaging is needed for final assessment. The six other assessment categories have implications on patient care. DISTINGUISHING BENIGN FROM MALIGNANT MASSESSection 5 of 10
Originally, US was primarily used to distinguish simple cysts, which did not require sampling, from solid masses that were usually examined with biopsy. Many of these biopsy samples were benign. Improving equipment and scanning techniques have helped expand the applications of breast US. Linear-array high-frequency (7.5 MHz or higher center frequency) transducers are generally used. Recent innovations include electronically steered compound imaging and tissue harmonic imaging. Contrast-enhanced Doppler US and 3-dimensional imaging are experimental techniques that are being evaluated. Classification of benign, indeterminate, and malignant nodules In a 1995 landmark study, Stavros et al established US criteria to characterize solid breast masses. This work was facilitated by evolving technical improvements in US equipment that provided better resolution and images. They demonstrated that US can be used to accurately classify some solid lesions as benign, allowing follow-up with imaging rather than biopsy. They used high-resolution transducers, which were state-of-the-art at that time, and performed examinations in both radial and antiradial planes. The investigators also focused on the evaluating suspected areas in the transverse and longitudinal planes. Stavros et al proposed a US scheme for prospectively classifying breast nodules into 1 of 3 categories: benign, indeterminate, or malignant. To be classified as benign, a nodule had to have no malignant characteristics and also demonstrate 1 of the 3 following combinations of benign characteristics: (1) intense uniform hyperechogenicity; (2) ellipsoid or wider-than-tall (parallel) orientation along with a thin, echogenic capsule; or (3) 2 or 3 gentle lobulations and a thin, echogenic capsule. A nodule is indeterminate by default if it had no malignant characteristics and none of the three previously listed benign characteristic combinations. To be classified as malignant, a mass needed to have any of the following characteristics: spiculated contour, taller-than-wide (not parallel) orientation, angular margins, marked hypoechogenicity, posterior acoustic shadowing, punctate calcifications, duct extension, branch pattern, or microlobulation. Of the 424 lesions that Stavros et al prospectively classified as benign by means of US only 2 were malignant at biopsy, resulting in a negative predictive value of 99.5% in a population with a cancer prevalence of 16.7%. Of the 125 lesions found to be malignant at biopsy, 123 were classified as malignant or indeterminate with US, for a sensitivity of 98.4%. Biopsy is indicated for nodules that are classified by US as either malignant or indeterminate. In 1998, Skaane et al found that US could distinguish fibroadenomas from invasive ductal carcinoma. Others who have studied the characteristics of benign and malignant masses by US examination include Zonderland et al and Rahbar et al. Typical US patterns of specific types of breast carcinomas The appearance of specific types of breast carcinoma has been studied. Although theirs appearance vary greatly, some patterns are typical. Mucin-containing carcinomas are often circumscribed but may have irregular margins. These lesions may be either hypoechoic or isoechoic relative to subcutaneous fat. Conant et al studied these carcinomas, and US showed hypoechoic, solid masses in all 8 of their cases. The lesions demonstrated acoustic shadowing or increased acoustic enhancement. Some had circumscribed margins, and some were not circumscribed. Tubular carcinoma is usually hypoechoic but without circumscribed margins and acoustic posterior shadowing. Invasive ductal carcinoma typically appears as an irregularly shaped mass with spiculated margins with shadowing and architectural distortion of adjacent breast tissue. This lesion may contain malignant microcalcifications. Invasive lobular carcinoma often does not cause a desmoplastic reaction. This type is a frequently missed on mammography and may be difficult to see on sonograms. Butler et al reported that these lesions were ultrasonographically occult in 12% of their cases. In approximately 60% of cases, it appeared as a heterogeneous, hypoechoic mass with angular or ill-defined margins and posterior acoustic shadowing. In 15% of cases, US demonstrated focal shadowing without a discrete mass, and in 12%, US showed a lobulated, circumscribed mass. Medullary carcinoma often appears as a hypoechoic mass with acoustic enhancement (increased through transmission). It can be mistaken for a cyst on US. Soo et al studied papillary carcinoma of the breast and found that the cystic in situ form can appear as either a solid mass or a complex cystic mass with an internal solid component. Both types tend to have increased acoustic enhancement. Doppler study may demonstrate intratumoral blood flow. Invasive papillary carcinoma usually appears as a solid mass, although it may also be a complex cystic and solid mass. Ductal carcinoma in situ of the breast often appears as suggestive microcalcifications on mammography. However, it may occasionally appear as a solid mass on US. Characteristic benign masses Many masses demonstrated on mammography require biopsy to determine if they are benign. Taylor et al showed that the addition of US to mammography could increase the specificity from 51% to 66% in a population with a malignancy prevalence of 31%. This improvement could significantly reduce the biopsy rate of benign lesions. Breast US often reveals unexpected benign lesions. Many benign breast conditions have a nonspecific US appearance. However, some masses, such as simple cysts, sebaceous cysts, and intramammary lymph nodes, have a characteristic appearance that suggests a specific diagnosis. Almost all highly echogenic masses are benign. If the contents within a complex cyst or dilated duct demonstrate blood flow on color Doppler imaging, then these contents consist of solid tissue rather then just debris, blood clot or echogenic fluid. However, we have seen solid tumors that lack demonstrable blood flow on color Doppler imaging. Several studies have reviewed the ability of color Doppler US or contrast-enhanced Doppler US to distinguish benign from malignant lesions. The results are variable and Doppler US is not generally used to distinguish benign from malignant solid breast masses. US-GUIDED PROCEDURES AND TREATMENTSSection 6 of 10
US is used to guide procedures, such as cyst aspiration, percutaneous biopsy, needle localization of masses for surgical excision, abscess drainage in selected cases, and therapeutic radiofrequency or cryoablation. US is highly accurate in diagnosing a simple cyst and helpful in evaluating some complex cysts. Usually, simple cysts are not aspirated unless they are symptomatic or of persistent psychological concern to the patient. Complex cysts or suspected abscesses may be aspirated. In 2003, Berg et al reviewed their experience with the US-pathologic correlation of cystic lesions. They found that all clustered microcysts were benign but cautioned that further study is required. They recommended that (1) cystic lesions with thick, indistinct walls and/or thick septations (0.5 mm); (2) intracystic masses; and (3) predominantly solid masses with eccentric cystic foci should be examined with biopsy because 18 of 79 of such complex cystic lesions proved to be malignant in their series. If it is uncertain whether a nodule seen on US is a complex cyst or solid mass, US-guided aspiration of the cyst is often performed. This procedure is also done if the US appearance of a complex cyst is of concern. The aspirate can be sent for cytologic evaluation, though there is no general consensus about the indications for cytology. Some clinicians send only the fluid for analysis if it is bloody. In 1993, Parker et al reported excellent concordance between the results of US-guided automated core biopsy with a 14-gauge needle and surgical resection in 49 lesions. US provides effective guidance for percutaneous breast biopsy without ionizing radiation. It also offers the advantages of real-time visualization of the needle and target lesion, multidirectional imaging, and low cost. It does not require the patient to undergo mammographic compression, and the patient can usually be recumbent rather than sitting, as is often needed for mammographic guidance of procedures. However, US is not appropriate for guidance in all situations. For instance, it is often not able to localize microcalcifications; in addition not all masses seen on mammography can be seen with US. Other biopsy devices, such as vacuum-assisted devices, have also been developed for use with US guidance. Occasionally, it may be difficult to find the area in the breast where core biopsy was previously performed. This may be a problem if the pathologic results from the biopsy sample and other factors indicate that excisional biopsy or lumpectomy is needed. After a patient receives preoperative neoadjuvant chemotherapy, the tumor may become occult, making it difficult to localize for lumpectomy. For these reasons, various US techniques to mark the biopsy or tumor site have been developed. These included the deployment of coils, clips, or wires. US-guided fine-needle aspiration biopsy (FNAB) of solid nodules has been used at many centers. Some advantages are that it is relatively easy for a skilled practitioner to perform and that the results are quickly obtained if a cytopathologist is available. The person performing the FNAB and the cytopathologist must be skilled for good results. Some groups have achieved excellent results. However, in 2001, Pisano et al reported their results form a study of 18 institutions in which US-guided or stereotactically guided FNAB yielded a 10% insufficient-sample rate for US-guided FNAB of masses. This finding does not compare favorably with results of US-guided core biopsy or US-guided needle localization. Several investigators have presented preliminary work in the use of US-guided therapeutic radiofrequency or cryoablation of invasive breast carcinoma. US IN TREATMENT PLANNING, SURGERY, AND POSTTREATMENT FOLLOW-UPSection 7 of 10
Berg et al showed the possible benefit of combining preoperative whole-breast US with mammography when breast-conservation surgery is planned. US demonstrated additional sites of multifocal and multicentric carcinoma, facilitating preoperative planning. Several investigators have studied US in assessing axillary lymph nodes for tumor involvement. Normal lymph nodes usually have a prominent echogenic fatty hilum and a thin hypoechoic cortex. Lymph nodes that lack a fatty echogenic hilum or are heterogeneous are considered suspicious. The US appearances of benign and malignant lymph nodes overlap; therefore US-guided FNAB of suspicious lymph nodes has been advocated. Krishnamurthy et al found that approximately 12% of cases have a false-negative result with US-guided axillary lymph node FNAB. In 2003, Deurloo et al showed that US-guided axillary lymph node FNAB reduces the number of the more time-consuming sentinel-node biopsy procedures that are needed. Intraoperative US may be used to localize breast masses. It obviates preoperative needle localization, offers more flexibility in choosing the incision site than preoperative needle localization, and may allow assessment of the tumor's extent. However, intraoperative US is operator dependent, and as with breast needle localization, it may not help in localizing the carcinoma. US also plays a role in the postoperative assessment of patients with breast cancer. It can be helpful in evaluating both postoperative breast masses and breast infections. Edeiken et al showed that US offers a benefit in the detection of recurrent cancer on breasts reconstructed with autogenous myocutaneous flaps. SPECIAL TOPICSSection 8 of 10
Breast implants Although MRI is accurate in evaluating silicone implants for rupture, MRI is not readily available or cannot be used in a number of circumstances. For instance, rupture of implants may be evaluated with US. On US, an intact implant has an echogenic wall and its contents are anechoic. Normal folds in the implant wall may be seen. US can demonstrate the stepladder sign consisting of multiple lines in the implant when an intracapsular rupture occurs or when an extracapsular rupture occurs, producing the snowstorm sign of increased echogenicity. US can provide additional information about implants, and it may also help in evaluating breast masses that are unrelated to the implant. Male breast LeukemiasIn the male patient, US may help in distinguishing benign conditions, such as gynecomastia, from breast carcinoma. Many believe that the addition of US to mammography increases diagnostic accuracy. However, US findings of malignancy in the male breast may be subtle, and the appearances of benign and malignancy disease overlap. Pediatric breast US is particularly helpful in characterizing cystic, inflammatory, and neoplastic lesions in children. Fibroadenomas are the most common breast tumors in adolescent girls and can become large. Although most masses that occur in the pediatric breast are benign, phyllodes tumors may be benign or malignant. In adolescents, cystosarcoma phyllodes are rare, but they are still the most common malignant breast tumors. Phyllodes tumors are usually well-circumscribed, oval or lobulated tumors, and they may have cystic areas. In their series of female adolescents, Kronemer et al found that the sonograms demonstrated 36 fibroadenomas, 12 cysts, 7 abscesses, 1 lactating adenoma, and 1 phyllodes tumor. Performing US of breast masses in pediatric and adolescent patients, Weinstein et al reported the following findings: gynecomastia, cyst, fibroadenoma, lymph node, galactocele, duct ectasia, and infection. They had no patients with malignancy but cautioned that, in rare cases, rhabdomyosarcoma, non-Hodgkin lymphoma, and leukemia may metastasize to the breast and that they are more likely to be present than a primary breast cancer in patients of this age group. MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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