The radiologic workup of a palpable breast mass
ABSTRACTThe finding of a palpable breast mass on physical examination often warrants a radiologic workup including directed ultrasonography, diagnostic mammography, and, at times, biopsy with ultrasonographic guidance. The choice of initial imaging study is most often guided by the patient’s age at presentation. Communicating the clinical findings to both the patient and the radiologist helps ensure the selection of the most appropriate imaging studies and helps in the interpretation of those studies. Every woman with a palpable breast mass, regardless of her age, should undergo imaging to exclude or establish the diagnosis of cancer.
KEY POINTS
- Typically, in women under age 30, ultrasonography is the first or the only test ordered to evaluate the abnormality. In women age 30 or older, diagnostic mammography is typically the first test ordered.
- On mammography, a suspicious palpable mass has an irregular shape with spiculated margins. A benign mass typically has a round shape with well-circumscribed margins.
- When mammography is required during pregnancy, the patient can be reassured that it will not jeopardize her fetus because the radiation dose is very low and the abdomen and pelvis can be shielded.
IMAGING TECHNIQUES
Mammography and ultrasonography are the primary imaging studies for evaluating palpable breast masses. Typically, in women under age 30, ultrasonography is the first or the only test ordered to evaluate the abnormality.4 In women age 30 or older, diagnostic mammography is typically the first test ordered. If mammography indicates that the palpable mass is not benign, then ultrasonography is the next study to be done.3 Although a powerful tool, magnetic resonance imaging of the breast does not currently have a role in the workup of a palpable abnormality and should not be used as a decision-delaying tactic or in place of biopsy.
Screening or diagnostic mammography?
Mammography is used in both screening and diagnosis. Screening mammography consists of two standard views of each breast—craniocaudal and mediolateral oblique—and is appropriate for asymptomatic women.
Women age 30 or older who present with a palpable breast mass require diagnostic mammography, in which standard mammographic views are obtained, as well as additional views (eg, tangential or spot-compression views) to better define the area of clinical concern. In a tangential view, a metallic skin marker is placed on the skin overlying the site of the palpable abnormality.
On mammography, a suspicious palpable mass has an irregular shape with spiculated margins. A benign mass typically has a round shape with well-circumscribed margins. If the palpable abnormality is not mammographically benign (eg, if it does not look like a lymph node, lipoma, or degenerating fibroadenoma), then ultrasonography is performed.
Mammography is less sensitive in younger women (ie, under age 30) because their breast tissue tends to be dense and glandular, whereas the tissue becomes more “fat-replaced” with age.3
Ultrasonography plays a complementary role
Ultrasonography complements diagnostic mammography and can be used as a first imaging study to evaluate a palpable breast mass in a young woman (ie, under age 30) with dense breast tissue. Ultrasonography is helpful in distinguishing cystic lesions from solid masses. It helps the radiologist delineate the shape, borders, and acoustic properties of the mass. It is also performed when a palpable mass is mammographically occult. When a mass appears suspicious on either mammography or ultrasonography, ultrasonography can be used to guide biopsy.
A suspicious mass on ultrasonography classically appears “taller than wide” and has posterior acoustic shadowing. Microlobulations and a spiculated margin also raise concern for malignancy. A benign sonographic appearance of a palpable mass includes a “wider than tall” (ellipsoid) shape, with homogeneous echogenicity, and four or fewer gentle lobulations. A thin, echogenic capsule also suggests the mass is benign.
Core-needle biopsy with ultrasonographic guidance
Core-needle biopsy is performed with a large-diameter (14-gauge to 18-gauge) needle to obtain tissue cores for histologic analysis. It has gained popularity over fine-needle aspiration because it includes surrounding tissue architecture, thus providing a more definitive histologic diagnosis.
Pathologic information obtained from core-needle biopsy allows the radiologist and surgeon to counsel the patient and determine the best surgical management or follow-up imaging study. If a clinician performs fine-needle biopsy in the office, it should be preceded by an imaging workup of the palpable finding.
WHAT IS APPROPRIATE FOR OUR 28-YEAR-OLD PATIENT?
Because she is under age 30, ultrasonography is the initial study of choice to evaluate the mass. If a simple cyst is detected, she can be reassured that the lesion is benign, and no subsequent follow-up is required. If the lesion is a solid mass with benign features, mammography may be considered, the patient may be followed with short-interval imaging (every 6 months) depending on patient-specific factors such as family history, or the mass can be biopsied. If the lesion is a solid mass with suspicious or malignant features, mammography with spot-compression views should be performed, and the patient should undergo core-needle biopsy with ultrasonographic guidance.
In a patient age 30 or older, diagnostic mammography is the imaging study of first choice.3 If the mass is clearly benign on mammography, no additional imaging would be necessary. If mammography fails to image the mass or shows it to have benign features such as fat, then the patient can undergo ultrasonography for further evaluation and confirmation of the clinical and mammographic findings. If the mass appears suspicious or malignant on mammography, ultrasonography is the next step, as it can help characterize the lesion and be used to guide core-needle biopsy.
