The role of ultrasound in breast imaging.
Abstract: This report describes several patients in whom diagnostic ultrasound played a significant role in the detection and diagnosis of breast masses. Diagnostic ultrasound was able to verify whether a breast mass was or was not present. Secondly, ultrasound was able to determine whether the mass was definitely benign and no further evaluation was necessary, or whether the mass was possibly malignant and needed a biopsy. The important role diagnostic ultrasound plays in breast imaging and its appropriate clinical applications are discussed.
Article Type: Report
Subject: Breast cancer (Diagnosis)
Breast cancer (Care and treatment)
Ultrasound imaging (Usage)
Cancer (Diagnosis)
Cancer (Methods)
Cancer (Technology application)
Authors: Hatfield, Ginger P.
Hogan, Michael T.
Pub Date: 10/01/2009
Publication: Name: West Virginia Medical Journal Publisher: West Virginia State Medical Association Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 West Virginia State Medical Association ISSN: 0043-3284
Issue: Date: Oct, 2009 Source Volume: 105 Source Issue: S1
Topic: Computer Subject: Technology application
Geographic: Geographic Scope: West Virginia Geographic Code: 1U5WV West Virginia
Accession Number: 218949144
Full Text: Objectives

To understand the value of diagnostic ultrasound in evaluation of breast disease.

To discuss the advantages and limitations of ultrasound when compared to other imaging modalities.

To explore when ultrasound should be used initially or as an adjunct in evaluating breast disease.

Cases

Case 1

A 44 year old woman presented with a palpable mass in the left breast. Mammogram revealed a mass in the same location as the palpable mass (Figure 1). Ultrasound was performed to determine whether the mass was cystic or solid, and, if solid, what its morphologic characteristics were. The mass was found to be a definite benign cyst, and further work-up was avoided. In order for a mass to be called a simple benign cyst, it must be anechoic, it must have a sharp posterior wall, it must have well circumscribed walls, and it must have good through transmission. All of these findings were present in this case, and biopsy was avoided (Figure 2).

Case 2

A 42 year old woman presented with a palpable abnormality in the left breast. The mammogram, including additional views, was negative. Because a mass is not always visible on a mammogram, an ultrasound study was performed. The ultrasound revealed normal breast tissue, with no evidence of mass. No further work-up was necessary, and the patient was discharged.

Case 3

A 48 year old woman presented with a palpable abnormality at the one o'clock position in the right breast. There was no family or personal history of cancer. The mammogram was negative (Figure 3). Because of the palpable abnormality, an ultrasound was performed, and this revealed a solid mass with malignant characteristics. None of the criteria necessary to call a mass a simple benign cyst were present, plus the mass had an irregular and lobulated border (Figure 4), characteristics of malignancy.

[FIGURE 1 OMITTED]

Discussion

The importance of diagnostic and screening mammography in the evaluation of breast disease is well known. However, the importance of diagnostic ultrasound in the evaluation of breast disease is less well known. This article discusses the important role ultrasound plays in breast imaging.

Ultrasound is a safe, painless, and also reliable, noninvasive modality for evaluation of the breast. It does not use ionizing radiation. Instead, sound waves are emitted from a handheld transducer that is held in direct contact with the breast skin surface. These emitted sound waves travel through the breast tissue, and when they encounter different tissue interfaces in the breast, they are reflected back to the same transducer. The acoustic impedance of the different tissues determines the characteristics of the waves that return to the transducer (1). The returning sound waves are then processed, and an image is formed.

Whenever there is a palpable mass in a patient under thirty years old, or in a pregnant or lactating woman, ultrasound should be the first modality used for further evaluation of the mass. Patients in these categories tend to have dense breasts, which are not well evaluated by mammography. The sensitivity of mammography decreases as breast density increases; therefore, lesions may not be detected by mammogram. The lack of ionizing radiation also makes ultrasound an ideal modality for evaluation of these patients.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Characterization of a mass found on mammography is the most frequent clinical use of breast ultrasound (2). Whenever a mass is discovered on a mammogram, ultrasound can determine whether the mass is a simple benign cyst, and the workup can be terminated, or whether the mass is solid, and biopsy may be necessary. The accuracy of breast ultrasound in differentiating a cystic from a solid mass has been reported as high as 98% to 100% (2). Using strict criteria, and if the classic signs are present, some solid masses can also be identified as benign. The classic ultrasound morphology of a lymph node is so distinctive that it can be called benign with no biopsy being necessary (3). If another benign-appearing solid mass is present, such as a fibroadenoma, it would be classified as probably benign. It would then be followed by ultrasound at six, twelve, and twenty-four months to verify stability (4). Using the Stavros criteria, a set of criteria used to assess solid, nonpalpable breast masses, a radiologist can obtain greater than 95% specificity for benignity, eliminating the need for biopsy (5). In a large study performed in 1995 by Stavros et al., strictly adhering to the Stavros criteria led to a negative predictive value of 99.5% and a sensitivity of 98.4% (2). Stavros described several benign and malignant characteristics of masses by ultrasound. Benign characteristics include having four or fewer gentle lobulations, intense homogeneous hyperechogenicity, a thin, echogenic capsule, and being wider than tall (2). The most important benign characteristic is having no malignant characteristics. If a mass has any of the malignant characteristics, it should be biopsied. Malignant characteristics include acoustic shadowing, microlobulation, microcalcifications, ductal extension, angulated margins, and intense hypoechogenicity (2).

If there is a palpable mass in a patient over thirty years old, and the mammogram is negative, ultrasound allows the radiologist to visualize the palpable area and to determine if it is caused by a solid mass, a cyst, or normal breast tissue. Especially in dense breasts, these entities are very difficult to distinguish on mammography. In addition, some masses that are completely occult on mammography can be visualized on ultrasound, as in Case 3. If normal breast tissue is visualized on the ultrasound, the workup is terminated. The negative predictive value of a negative mammogram combined with a negative ultrasound has been found to be almost 100%, in the setting of a clinically palpable finding (5). If a cyst or normal lymph node is seen, the work up is also terminated. If another benign appearing solid mass is diagnosed, follow-up by ultrasound is recommended. If any other solid mass is seen, biopsy is necessary.

Ultrasound is also used to evaluate silicone implants for possible rupture. Ultrasound is more sensitive for detection of silicone implant rupture than mammography, but less sensitive than MRI. If there are classic findings of implant rupture on ultrasound, the patient can be spared the expense of an MRI. If there is solid clinical suspicion for implant rupture with a negative ultrasound, MRI should then be considered (5).

Some masses are seen very well with two-view mammography; in these cases, stereotactic biopsy could be employed. However, many masses are seen better with ultrasound, or are not seen at all on a mammogram. In such cases, ultrasound can be used by the radiologist for visual guidance in obtaining a sample for pathologic evaluation. Ultrasound can be used for both fine needle aspiration and core biopsy (6). A vacuum-assisted biopsy device can also be employed during ultrasound-guided biopsy (7).

Being familiar with the limitations of ultrasound is just as important as being aware of the common applications. Ultrasound is not a screening procedure, and should not be used for annual screening (5) Mammography is the modality used for annual screening, as it is the only modality at this time that has been shown to reduce breast cancer related death rates (9). Ultrasound is also not the modality of choice for evaluating calcifications. Calcifications are a very important finding associated with several benign and malignant conditions involving the breast, and evaluation of their size, shape, and distribution in determining benignity or malignancy should be assessed by mammography, and not ultrasound. Calcifications can often not be seen on ultrasound, and if they are seen, the important characteristics that allow a radiologist to assess for malignancy cannot be accurately assessed.

Conclusion

Ultrasound is a very attractive and essential breast imaging modality.

It is safe, painless, reliable, and noninvasive. For a patient under thirty years old, or for a pregnant or lactating woman, it should be the first breast imaging procedure used to evaluate a breast mass. As an adjunct to mammography or palpation, it can accurately distinguish normal breast tissue, a simple benign cyst, a benign solid mass, a probably benign solid mass, or a solid mass that requires biopsy. Whether as a starting point, or as an adjunct to mammography and palpation, ultrasound is a crucial component in the evaluation of breast disease.

CME Post-Test

38. The first imaging procedure that should be used to evaluate a new lump in a 28 year old is:

a. Mammography

b. Ultrasound

c. MRI

d. CT

39. Which imaging modality is the only one proven to decrease mortality due to cancer related deaths when used for annual screening?

a. Mammography

b. Ultrasound

c. MRI

d. CT

40. Which imaging modality should be used initially in evaluation of a pregnant woman with a palpable mass?

a. Mammography

b. Ultrasound

c. MRI

d. CT

41. Which of the following is a malignant characteristic on ultrasound?

a. Four or fewer gentle lobulations

b. Intense, homogeneous hyperechogenicity

c. Thin, echogenic capsule

d. Shadowing

References

(1.) Cardenosa G. Breast Imaging (The Core Curriculum Series). 1st ed. Philadelphia, PA: Lippincott Williams and Wilkins: 2004.

(2.) Ikeda DM. Breast Imaging: The Requisites. 1st ed. Philadelphia, PA: Elsevier; 2004.

(3.) Cardenosa G. Clinical Breast Imaging: A Patient Focused Teaching File. 1st ed. Philadelphia, PA: Lippincott Williams and Wilkins: 2007.

(4.) Mendelson EB. Breast Ultrasound: Technique, Equipment, Performance, and Pitfalls. Allegheny General Hospital, Pittsburgh Breast Imaging Seminar [DVD]. Birmingham, AL: Oakstone Medical Publishing; 2007.

(5.) Conant EF, Brennecke CM. Breast Imaging: Case Review Series. 1st ed. Philadelphia, PA: Mosby; 2006.

(6.) Oktay A. Ultrasound Guided Breast Biopsies and Aspirations. Ultrasound Clinics. 2008; 3: 289-294.

(7.) Povoski SP, Jimenez RE. A comprehensive evaluation of the 8-gauge Vacuum-assisted Mammotome[R] system for ultrasound-guided diagnostic biopsy and selective excision of breast lesions. World J Surg Oncol. 2007; 5:83.

(8.) Kopans DB. Breast Imaging. 2nd ed. Philadelphia, PA: Lippincott-Raven; 1998.

(9.) Berg WA. Rationale for a Trial of Screening Breast Ultrasound: American College of Radiology Imaging Network (ACRIN) 6666. AJR. 2003;180: 1225-1228.

Ginger P. Hatfield, MD

Radiology Resident

Michael T. Hogan, MD

Associate Professor of Radiology, West Virginia

University School of Medicine
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