A. Screening for breast cancer. Screening mammogram
Screening for breast cancer. Screening mammogram lowers mortality from breast cancer. It is performed in the asymptomatic patient and consists of two standard views, mediolateral oblique (MLO) and craniocaudal (CC). The current recommendation from the National Cancer Institute and American College of Surgeons is annual screening mammography for women aged 40 years and older. Breast lesions on mammograms are classified according to the American College of Radiology by BI-RADS (Breast Imaging Reporting and Database System) scores:
- 0 = Needs further imaging; assessment incomplete.
- 1 = Normal; continue annual follow-up (risk of malignancy: 1/2,000).
- 2 = Benign lesion; no risk of malignancy; continue annual follow-up (risk of malignancy: 1/2,000).
- 3 = Probably benign lesion; needs 4 to 6 months follow-up (risk of malignancy: 1% to 2%).
- 4 = Suspicious for breast cancer; biopsy recommended (risk of malignancy: 25% to 50%).
- 5 = Highly suspicious for breast cancer; biopsy required (75% to 99% are malignant).
- 6 = Known biopsy-proven malignancy.
1.Malignant mammographic findings
- New or spiculated masses.
- Clustered microcalcifications in linear or branching array.
- Architectural distortion.
2.Benign mammographic findings
- Radial scar. Generally due to fibrocystic breast condition (FBC); associated with proliferative epithelium in the center of the fibrotic area in approximately one third of cases. Appearance often mimics malignancy; a biopsy is needed to rule out malignancy.
- Fat necrosis. Results from local trauma to the breast. It may resemble carcinoma on palpation and on mammography. The fat may liquefy instead of scarring, which results in a characteristic oil cyst. A biopsy may be needed to rule out malignancy.
- Milk of calcium. Associated with FBC; caused by calcified debris in the base of the acini. Characteristic microcalcifications appear discoid on craniocaudal view and sickle-shaped on mediolateral oblique view. These are benign and do not require biopsy.
- Cysts cannot be distinguished from solid masses by mammography; ultrasound is needed to make this distinction.
3.Screening in high-risk patients:
For patients with known BRCA mutations, annual mammograms and semiannual physical examinations should begin at age 25 to 30 years. In patients with a strong family history of breast cancer but undocumented genetic mutation, annual mammograms and semiannual physical examinations should begin 10 years earlier than the age of the youngest affected relative and no later than age 40 years.
4.Magnetic resonance imaging (MRI) is recommended for screening in selected high-risk patients with:
- A lifetime risk of breast cancer greater than 20% as defined by available risk assessment tools (e.g., BRCAPRO, Gail, Claus, and Tyrer-Cuskick models).
- BRCA mutations.
- A first-degree relative (parent, sibling, child) with a BRCA1 or BRCA2 mutation.
- History of radiation to the chest wall between the ages of 10 to 30 years (e.g., Hodgkin lymphoma patients).
- Li-Fraumeni, Cowden, or Bannayan-Riley-Ruvalcaba syndromes.
B. Diagnostic imaging
1.Diagnostic mammograms are performed in the symptomatic patient or to follow up on an abnormality noted on a screening mammogram. Additional views (spot-compression views or magnification views) may be used to further characterize any lesion. The false-negative and false-positive rates are both approximately 10%. A normal mammogram in the presence of a palpable mass does not exclude malignancy and further workup should be performed with an ultrasound, MRI, and/or biopsy.
2.Ultrasonography is used to further characterize a lesion identified by physical examination or mammography. It can determine whether a lesion is solid or cystic and can define the size, contour, or internal texture of the lesion. Although not a useful screening modality by itself due to significant false-positive rates, when used as an adjunct with mammography, ultrasonography may improve diagnostic sensitivity of benign findings to greater than 90%, especially among younger patients for whom mammographic sensitivity is lower due to denser breast tissue. In those patients with a known cancer, ultrasound is sometimes used to detect additional suspicious lesions and/or to map the extent of disease.
3.MRI is useful as an adjunct to mammography to determine extent of disease, to detect multicentric disease in the dense breast, to assess the contralateral breast, to evaluate patients with axillary metastases and an unknown primary, and in patients in whom mammogram, ultrasound, and clinical findings are inconclusive. It is also useful for assessing chest wall involvement.