Breast

• Adenosis or lobulocentric processes with increase in glandular elements of terminal duct lobular unit (TDLU) with stromal fibrosis / sclerosis that distorts and compresses glands
• Preserved 2 cell layer (inner epithelial and outer myoepithelial cells)

• Most frequent in third to fourth decades but occurs over a wide age range
• Found in 12 - 28% of all benign and 5 - 7% of malignant biopsies (J Ultrasound Med 2013;32:2029)

• Considered a part of the spectrum of fibrocystic changes
• Often an incidental finding or detected by screening
• Can present as a palpable mass if nodular adenosis / adenosis tumor
• Reference: Schnitt: Biopsy Interpretation of the Breast, 3rd Edition, 2017

Contributed by Julie M. Jorns, M.D.

• As a single feature, increased risk of cancer of 1.5 - 2x, as seen with proliferative fibrocystic changes (Cancer 1989;64:1977)
• 2x higher risk of breast cancer with increased Ki67 proliferation index in sclerosing adenosis or associated normal background breast tissue (Breast Cancer Res Treat 2015;151:89)
• Does not provide further risk stratification in the presence of other proliferative disease / atypical hyperplasias (Breast Cancer Res Treat 2014;144:205)
• Rarely involved by lobular carcinoma in situ and mistaken for invasive carcinoma (Mod Pathol 1991;4:1)
• Ductal carcinoma in situ arising in sclerosing adenosis has a higher frequency of bilaterality (Clin Breast Cancer 2012;12:398, Breast Cancer 2014;21:732)
• Can mimic malignancy clinically and radiologically

• 46 year old woman with sclerosing adenosis with mammogram and cytology mimicking malignancy (J Cytol 2013;30:49)
• 73 year old woman with sclerosing adenosis and coexisting ductal carcinoma in situ (Int J Surg Case Rep 2018;45:9)
• 82 year old woman with sclerosing adenosis in sentinel axillary lymph nodes (Arch Pathol Lab Med 2008;132:1439)

• Presence of sclerosing adenosis alone in a core biopsy does not require surgical excision
• Coexisting atypia will typically prompt surgical consultation

Contributed by Julie M. Jorns, M.D.

A premenopausal woman underwent breast biopsy for screening detected microcalcifications showing the pictured lesion. This lesion typically is associated with

1. Abundant cytologic atypia
2. Clinically palpable mass
3. Lack of myoepithelium
4. Variable imaging features

D. Variable imaging features. The pictured lesion is sclerosing adenosis, a benign breast lesion characterized by expansion of glands (with preserved 2 cell layers: inner epithelial and outer myoepithelial cells) within the terminal duct lobular unit with distortion by fibrosis / sclerosis. Most of the time, sclerosing adenosis lacks cytologic atypia. Sclerosing adenosis frequently has calcifications due to entrapped secretions. However, when abundant, sclerosing adenosis may present as a distortion or mass on imaging. Sometimes sclerosing adenosis clinically presents as a palpable mass, as with nodular adenosis / adenosis tumor. However, sclerosing adenosis can often be an incidental finding when there is another indication for biopsy. Thus, imaging findings are variable, depending on size and extent of the lesion.

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Reference: Sclerosing adenosis

Sclerosing adenosis of the breast (without atypia) imparts what risk for future breast cancer?

1. No increased risk
2. 1.5 - 2x increased risk
3. 4 - 5x increased risk
4. 8 - 10x increased risk bilaterally
5. 8 - 10x increased risk ipsilaterally

B. 1.5 - 2x increased risk. Sclerosing adenosis is considered part of the spectrum of proliferative fibrocystic changes, which imparts a 1.5 - 2x increased risk for future breast cancer. This is opposed to nonproliferative fibrocystic change which has no increased risk and atypical ductal hyperplasia (ADH) with 4 - 5x, ductal carcinoma in situ (DCIS) with 8 - 10x (unilateral: ipsilateral side) and lobular carcinoma in situ (LCIS) with 8 - 10x (bilateral) increased risk for breast cancer.

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Reference: Sclerosing adenosis