Screening: X-ray mammography
Due to the high incidence of breast cancer among older women, screening is now recommended in many countries. Recommended screening methods include breast self-examination and mammography. Mammography has been estimated to reduce breast cancer-related mortality by 20-30%.Routine (annual) mammography of women older than age 40 or 50 is recommended by numerous organizations as a screening method to diagnose early breast cancer and has demonstrated a protective effect in multiple clinical trials.
The U.S. National Cancer Institute recommends screening mammography with a baseline mammogram at age 35, mammograms every two years beginning at age 40, and then annual mammograms beginning at age 50. In the UK, women are invited for screening once every three years beginning at age 50. Women with one or more first-degree relatives (mother, sister, daughter) with premenopausal breast cancer should begin screening at an earlier age. It is usually suggested to start screening at an age that is 10 years less than the age at which the relative was diagnosed with breast cancer.
Part of the difficulty in interpreting mammograms in younger women stems from the problem of breast density. Radiographically, a dense breast has a preponderance of glandular tissue, and younger age or estrogen hormone replacement therapy contribute to mammographic breast density. After menopause, the breast glandular tissue gradually is replaced by fatty tissue, making mammographic interpretation much more accurate.
Breast density is an independent adverse prognostic factor on breast cancer prognosis.
Mammography is the modality of choice for screening of early breast cancer, since it is relatively fast, reasonably accurate, and widely available in developed countries. Breast cancers detected by mammography are usually much smaller (earlier stage) than those detected by patients or doctors as a breast lump.
Breast MRI
Magnetic resonance imaging (MRI) has been shown to detect cancers that are not visible on mammograms, but it has several disadvantages. For example, although it is 27-36% more sensitive, it is less specific than mammography. As a result, MRI studies will have more false positives (up to 5%), which may have undesirable financial and psychological costs. It is also a relatively expensive procedure, and one which requires the intravenous injection of a chemical agent to be effective.An MRI will be used if the patient has:
- Strong family history of breast cancer
- Patients with BRCA-1 or BRCA-2 oncogene mutations
- Evaluation of women with breast implants
- History of previous lumpectomy or breast biopsy surgeries
- Axillary metastasis with an unknown primary tumor
- Very dense or scarred breast tissue
Breast ultrasound
Ultrasound alone is not usually employed as a screening tool but it is a useful and pain free tool for the characterization of palpable tumours and directing image-guided biopsies.Breast self-exam
Breast self-exam was widely discussed in the 1990s as a useful modality for detecting breast cancer at an earlier stage of presentation. In studies in China it was concluded that women who had been taught self-exam tended to detect more breast nodules, but their breast cancer mortality rate was no different from that of women in the control group. In other words, women taught breast self-exam were mostly likely to detect benign breast disease, but were just as likely to die of breast cancer.Diagnosis
The diagnosis of breast cancer is established by the microscopic examination of surgically removed breast tissue.A number of procedures can obtain tissue or cells prior to definitive treatment for histological or cytological examination. Such procedures include fine-needle aspiration, nipple aspirates, ductal lavage, core needle biopsy, and local surgical excisional biopsy. These diagnostic steps, when coupled with radiographic imaging, are usually accurate in diagnosing a breast lesion as cancer.
Imaging tests are sometimes used to detect metastasis and include chest x-ray, bone scan, CT, MRI, and PET scanning. While imaging studies are useful in determining the presence of metastatic disease, they are not in and of themselves diagnostic of cancer. Only microscopic evaluation of a biopsy specimen can yield a cancer diagnosis.
Types of Breast Cancer
These are the pathological and clinical categories of breast cancer. There can be overlap between these categories; for example, a ductal carcinoma can also be an inflammatory breast cancer.- Ductal carcinoma 65-90%
- Lobular carcinoma 10%
- Inflammatory breast cancer
- Medullary carcinoma of the breast 5%
- Colloid carcinoma 2%
- Papillary carcinoma 1%
- Metaplastic carcinoma
- Triple Negative Breast Cancer
Staging
Breast cancer is staged according to the TNM system. Prognosis is closely linked to results of staging, and staging is also used to allocate patients to treatments both in clinical trials and clinical practice.Summary of stages:
- Stage 0 - Carcinoma in situ
- Stage I Tumor (T) does not exceed 2 cm, no axillary lymph nodes (N) involved.
- Stage IIA T 2-5 cm, N negative, or T <2 cm and N positive.
- Stage IIB T > 5 cm, N negative, or T 2-5 cm and N positive (< 4 axillary nodes).
- Stage IIIA T > 5 cm, N positive, or T 2-5 cm with 4 or more axillary nodes
- Stage IIIB T has penetrated chest wall or skin, and may have spread to < 10 axillary N
- Stage IIIC T has > 10 axillary N, 1 or more supraclavicular or infraclavicular N, or internal mammary N.
- Stage IV – Distant metastasis (M)
