11th April 2024

Benign Breast Diseases

Benign Breast Diseases

Anatomy

The three main structures that make up the breast include the skin, subcutaneous tissue, and breast tissue. The latter is composed of both epithelial and stromal elements. The epithelial element is made up of the ductal network, and the stroma contains adipose and fibrous connective tissue. Benign breast disease can affect any of these structures. 

Benign epithelial breast lesions can be classified into three histological categories. Non-proliferative, proliferative without atypia and proliferative with atypia.

Non-proliferative lesions

The commonest non-proliferative breast lesions are breast cysts. A breast cyst is a fluid-filled circular or ovoid mass derived from the terminal duct lobular unit. They are classified as simple, complex or complicated based on their sonographic features. The management of a breast cyst is guided by an imaging classification score (see investigation subheading below). In summary, for a simple cyst, no further intervention is necessary. Fine needle aspiration (FNA) is only performed when there are signs of infection. The management of a complicated cyst depends on the imaging classification score. A complex cyst requires core needle biopsy (CNB) for diagnosis.

Galactoceles, also known as milk retention cysts, are collections caused by an obstructed milk duct. These occur almost exclusively in lactating women. Ultrasound may show features of a complex mass. Aspiration yields a milky substance. There is no increased risk of subsequent breast cancer, and excision is not necessary. 

Other non-proliferative changes include papillary apocrine change and mild hyperplasia of the usual type.

Proliferative lesions without atypia

An intraductal papilloma is a multitude of papillary cells that grow from the wall of a duct into its lumen. Solitary intraductal papillomas may present with nipple discharge, with bloody discharge being a common presentation. Solitary lesions can be identified on ultrasound, mammography and MRI. After imaging, a CNB can be performed. Solitary papillomas without atypia and with imaging concordance do not require excision, and patients will likely be offered follow-up. Excision may be performed for symptomatic relief. Multiple papillomas (henceforth, diffuse papillomatosis) are defined as five or more papillomas within a localised segment of breast tissue. Definitive management is excision, as the risk of subsequent breast cancer is not well defined. 

Sclerosing adenosis is a benign lobular lesion featuring interspersed glandular cells and increased fibrous tissue. It can present as a suspicious finding on mammography. It is benign in itself but associated with an increased risk of future breast cancer compared to the general population. There is currently no single treatment approach or screening recommendation for sclerosing adenosis without atypia. Complex sclerosing lesions (also known as radial scars) are usually incidental discoveries on biopsy or excision. They are characterised by a fibroelastic core with radiating ducts and lobules. Complex lesions identified on biopsy should be excised. 

Fibroadenomas are the commonest benign breast tumour. They are well-defined, mobile on examination, and appear as solid masses on ultrasound scans. The exact aetiology is not known; however, hormones likely play a role. Definitive diagnosis can only be confirmed with a CNB (or excision). Simple fibroadenomas contain both glandular and fibrous tissue. Excision is not necessary in all cases; asymptomatic biopsy-proven simple fibroadenomas can be ignored. Complex fibroadenomas have histopathological proliferative changes. Examples of these proliferative changes include sclerosing adenosis, duct epithelial hyperplasia and epithelial calcification. There is no consensus on the management of complex fibroadenomas, CNB versus complete excision, and a case-by-case approach is adopted. 

Adenomas are pure epithelial breast tumours. Their sparse stromal elements distinguish them from fibroadenomas. The two main groups are tubular and lactating adenomas.

Proliferative lesions with atypia

These lesions are associated with an increased risk of developing breast cancer. Examples include atypical ductal hyperplasia, atypical lobular hyperplasia and lobular carcinoma in situ. The focus of management for these high-risk lesions is careful surveillance.

Miscellaneous

Lipomas are benign tumours made up of mature fat cells only. There is an absence of histologic elements of breast tissue. They are usually solitary, presenting as well-circumscribed, soft, non-tender masses. Core or excisional biopsy can be performed. There is no increased risk of subsequent breast cancer.

Fat necrosis typically occurs secondary to breast trauma or surgical intervention. Experienced radiologists can identify this pathology on ultrasound and/or mammogram. If the diagnosis is established, excision is not necessary. No increased risk of subsequent breast cancer. 

Periductal mastitis is an inflammatory condition affecting the subareolar ducts. The inflamed ducts are susceptible to secondary infection and formation of a subareolar abscess. Another rare inflammatory breast pathology affecting young women is idiopathic granulomatous mastitis. Breastfeeding women can develop lactational mastitis. If left untreated, this can progress to a secondary breast abscess. 

There are numerous congenital abnormalities of breast development. Polythelia, an accessory or supernumerary nipple, is seen in both sexes and is the most common variant of supernumerary breast components. An ectopic nipple may occur at any point from the axilla to the groin along the “milk streak.” Polymastia is accessory or supernumerary breast tissue. It is most commonly found in the axilla. Other rarer abnormalities include underdevelopment (hypoplasia), congenital absence (amastia) and the absence of breast tissue but a normal nipple-areola complex (amazia). 

Idiopathic granulomatous mastitis (IGM) is a benign, rare inflammatory disease of the breast. It typically affects younger women and presents as a unilaterally and peripheral breast lump. It can have malignant-like features on examination. Core needle biopsy shows non-necrotising granulomas. The most commonly isolated species is Corynebacterium kroppenstedtii.

Investigations

Ultrasound, mammography and MRI are used in the assessment of breast lesions. The imaging results will identify which lesions should undergo biopsy. The British Society of Breast Radiologists (BSBR) have a standardised classification system for breast lesions. A five-point scale is used to classify lesions from normal (1) to highly suspicious for malignancy (5). The breast imaging-reporting and data system (BI-RADS) is another classification system widely used in North America and Europe. A biopsy is recommended for all suspicious lesions (BSBR/BI-RADS 4 or 5). Biopsy under ultrasound guidance is preferred over alternative imaging modalities. A marker clip should be placed to assist with post-biopsy management (including repeat imaging). 

There are three biopsy methods: FNA, CNB and surgical biopsy. CNB is the preferred initial method in most cases. The benefit of CNB is that it is minimally invasive and usually acquires enough tissue to adequately assess the intended lesion. FNA demonstrates higher rates of insufficient tissue samples and false negative results. In these cases, CNB is required (following FNA). Surgical biopsy is performed if needle biopsy is not technically possible or the results of needle biopsy are inconclusive or discordant. The entire lesion can be removed (excisional biopsy), or a portion of the lesion can be removed (incisional biopsy). 

Complications of CNB include haematomas, infection, pneumothorax, fistula formation and potential seeding of tumour along the biopsy track.

References

• Radiopaedia. BSBR breast imaging classification. Last updated 15th December 2022. Available at https://radiopaedia.org/articles/bsbr-breast-imaging-classification 
• UpToDate. Breast biopsy. Last updated 28th April 2021. Available at https://www.uptodate.com/contents/breast-biopsy 
• UpToDate. Breast cysts: clinical manifestations, diagnosis and management. Last updated 12th April 2022. Available at https://www.uptodate.com/contents/breast-cysts-clinical-manifestations-diagnosis-and-management 
• UpToDate. Breast development and morphology. Last updated 7th June 2022. Available at https://www.uptodate.com/contents/breast-development-and-morphology 
• UpToDate. Breast masses in children and adolescents. Last updated 14th June 2022. Available at https://www.uptodate.com/contents/breast-masses-in-children-and-adolescents 
• UpToDate. Clinical manifestations, differential diagnosis, and clinical evaluation of a palpable breast mass. Last updated 20th August 2021. Available at https://www.uptodate.com/contents/clinical-manifestations-differential-diagnosis-and-clinical-evaluation-of-a-palpable-breast-mass 
• UpToDate. Common problems of breastfeeding and weaning. Last updated 29th March 2023. Available at https://www.uptodate.com/contents/common-problems-of-breastfeeding-and-weaning 
• UpToDate. Nipple discharge. Last updated 28th February 2022. Available at https://www.uptodate.com/contents/nipple-discharge
• UpToDate. Nonlactational mastitis in adults. Last updated 4th October 2022. Available at https://www.uptodate.com/contents/nonlactational-mastitis-in-adults 
• UpToDate. Overview of benign breast diseases. Last updated 23rd February 2023. Available at https://www.uptodate.com/contents/overview-of-benign-breast-diseases 
• UpToDate. Primary breast abscess. Last updated 9th August 2022. Available at https://www.uptodate.com/contents/primary-breast-abscess