Primer on the Management of Benign Breast Diseases
septations or mural thickening on imaging) are nearly always benign, they require aspiration only if bothersome to the patient.
Mild hyperplasia of the usual type is defined histologically as containing multiple duct epithelial cell layers (four or fewer) that do not obstruct the duct lumen. This entity has not been shown to confer an increase in breast cancer risk.
Proliferative Breast Lesions without Atypia Proliferative lesions without atypia include fibroadenomas, usual ductal hyperplasia (also called moderate or florid hyperplasia of the usual type), sclerosing adenosis, tubular adenomas, lactating adenomas, intraductal papillomas, and radial scars.22
Phyllodes tumors can also be
considered in this category, though rarely they behave as aggressive malignant lesions (discussion to follow).
Fibroadenomas are the most common cause of breast masses in adolescents and young women. The median age for presentation is 25 years. They also account for 12 % of masses in menopausal women. Fibroadenomas arise from the epithelium and stroma of the terminal duct lobular unit. They are typically characterized clinically as small (1–2 cm), firm, mobile, and well-circumscribed masses, though larger masses (3–6 cm) are occasionally seen. Multiple fibroadenomas may be present in approximately 15 % of cases.
Ultrasound is valuable in distinguishing fibroadenomas (a solid mass) from breast cysts (thin-walled, fluid-filled masses), as these entities may have similar palpable characteristics on exam and both appear as circumscribed masses on mammography. Importantly, whereas simple breast cysts may be observed without diagnostic or therapeutic aspiration, solid breast masses almost always require diagnostic evaluation via fine-needle aspiration (FNA) for cytology (in appropriate circumstances) or biopsy. Imaging alone cannot definitively distinguish benign fibroadenomas from malignant masses.
The term ‘giant fibroadenoma’ is often used to describe very large fibroadenomas, but they are histologically identical to common fibroadenomas. Juvenile fibroadenomas are an unusual variant that grows rapidly and often distorts the breast. Though composed of the same epithelial and stromal elements, they tend to have more florid glandularity and greater stromal cellularity.
Phyllodes tumours may present similarly to fibroadenomas as a rapidly enlarging, well-circumscribed and mobile breast mass. The average woman with a phyllodes tumor is between 30 and 50 years old. These uncommon fibroepithelial tumours, accounting for only 0.3–0.5 % of breast tumors, typically behave in a benign fashion. Only 5 % of phyllodes tumors behave as malignant sarcomas with the ability to produce distant metastases.23
Though FNA and core needle
biopsy are routinely used methods of evaluation of solid breast masses, excision should be considered if the cytopathologist suspects a phyllodes tumor. Not only is it difficult to distinguish between fibroadenomas and phyllodes tumors using FNA, phyllodes tumors may recur locally and therefore wide excision with 1 cm or greater margins is recommended for definitive treatment.23,24
US OBSTETRICS & GYNECOLOGY
Tubular adenomas often present as breast masses, but may also be identified on routine screening imaging. They are composed of benign glandular epithelial cells with minimal stroma. Lactating adenomas present as masses during pregnancy and lactation. They consist of cuboidal glandular cells, identical to normal lactating breast tissue. Both entities are solid masses on imaging, and require biopsy for histologic diagnosis.
Intraductal papillomas are common proliferative lesions. Women with centrally located intraductal papillomas frequently present with serous or serosanguinous nipple discharge, though they do present rarely as a palpable masses. Less commonly, intraductal papillomas can be multiple and peripheral, where they are most likely to be identified through routine screening breast imaging. Unlike solitary intraductal papillomas, women with multiple, peripheral papillomas are typically younger, may have bilateral involvement and either have co-existing breast cancer or a future breast cancer diagnosis in one-third of cases. The typical papilloma is 2–4 mm in size, though larger masses up to 5 cm have been described.
Usual ductal hyperplasia, or moderate hyperplasia of the usual type, is distinct from mild hyperplasia because it consists of greater than four cell layers, typically fills the duct and may dilate the involved duct. The cells have a benign appearance.
Atypical Hyperplasias
ADH and ALH are most commonly diagnosed as a result of abnormal breast imaging. They are identified in 2–4 % of women with breast masses on mammography and 12–17 % of women who underwent biopsy due to microcalcifications.11,25
Numerous studies have shown that
these women have a greater than 20 % lifetime risk of breast cancer.12 Subsequent breast cancers can occur in either breast and therefore counselling and close surveillance are appropriate.
Based on evidence from the National Surgical Adjuvant Breast and Bowel Project (NSABP) P-1 trial and its successors, these women may reduce their risk of future breast cancer by approximately 50 % by taking five years of use of selective estrogen receptor modulators (tamoxifen and raloxifene), and more recent evidence suggests aromatase inhibitors in menopausal women may be similarly protective.14–16,26
Lobular Carcinoma in Situ
LCIS is a microscopic diagnosis that typically does not have a clinical correlate (i.e. it does not present as a breast mass, nor can it typically be seen on breast imaging). It is most often identified incidentally in tissue sampled for evaluation of another lesion. It is generally not considered to be a precursor to invasive cancer (unlike ductal carcinoma in situ [DCIS]) but, like atypical hyperplasias, is a marker for increased invasive breast cancer risk in the future. Complete excision of LCIS is not indicated as it is not considered a precursor lesion, and it is frequently multifocal in the identified breast (greater than 50 % of cases) as well as the contralateral breast in 30 % of cases. Women with LCIS have a 1–2 % risk per year of developing invasive breast cancer and an estimated lifetime risk of 30–40 %. Subsequent cancers are just as likely in the contralateral breast as the breast in which it was diagnosed.27 Counselling, close surveillance and risk reduction medications are typically recommended for these women. Addition of magnetic
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