Abnormalities found on mammographic screening may need further evaluation with additional mammographic views or other imaging modalities, such as ultrasound or magnetic resonance imaging (MRI). In some screening programs, the mammograms are reviewed by the radiologist as they are performed, and if additional views are needed, they are performed on the same day. In other settings, the initial two-view screening mammogram is performed, and if additional studies are required, the patient is called back for them at a later date. In several studies, the frequency of “call-backs” has 26-32 ranged from 5-11%.
A variety of diagnostic views can be performed to evaluate breast lesions.
Coned compression views, mammographic images of a limited area, are useful in distinguishing a mass from a confluence of normal glandular structures or in separating out a mass from overlying parenchymal tissue.
They may be helpful in assessing an area of concern on the mammogram or an area of questioned palpable abnormality. Special projections can be used to image certain areas: exaggerated craniocaudal views image the axillary tail, cleavage views image the medial breast, and 30° oblique views image the axilla. Rolled craniocaudal views may help localize a lesion seen on only the craniocaudal projection, and a 90° lateral view may help determine the location of a lesion seen only on the mediolateral oblique projection. Magnification views are helpful to assess the margins of masses and to evaluate the morphology of calcifications.
Ultrasound is used primarily in three settings:
- to evaluate a focal mass identified on the mammogram that has circumscribed (smooth), obscured or indistinct borders
- to evaluate a palpable lump
- to guide interventional procedures
Ultrasound can distinguish a cyst, or fluid-filled mass, from a solid lesion.
The criteria for a simple cyst include a round or oval shape, a thin wall, the absence of internal echoes and the presence of posterior acoustic enhancement.
Although previously the primary use of ultrasound was in distinguishing cystic from solid lesions, recent work has suggested that ultrasound may also be helpful in characterizing solid masses in the breast.
The role of magnetic resonance imaging in the evaluation of breast lesions is still evolving. At the current time, MRI is used primarily in selected settings, such as in the identification of the primary carcinoma in women with breast carcinoma in an axillary node with a normal mammogram and physical examination. Early work suggests that MRI may be useful in women with known or suspected breast cancer to assess for the presence of multifocal or multicentric disease, to evaluate for involvement of the skin or chest wall and to distinguish scar tissue from recurrent carcinoma.
Laura Liberman and Timothy L. Feng
Breast cancer detection demonstration project: five-year summary report. CA 2003