Breast

• Benign tumor composed of distorted glands in a sclerotic stroma surrounded by a fibrous capsule
• First described by Azzopardi and Salm in 1984 (J Pathol 1984;144:15)

• Rare, benign adenomatous lesion of medium and small sized ducts in the peripheral breast
• Well circumscribed, single (occasionally multinodular), solid proliferation of tubules set within a fibrous stroma and surrounded by a thickened fibroelastotic wall
• Considered a highly sclerotic variant of intraductal papilloma with obliterated papillary growth
• May show calcifications, hemorrhage, infarction, squamous or apocrine metaplasia, epithelial hyperplasia, myxoid or chondroid change, central scar or pseudoinfiltrative pattern (exclude invasion by showing intact myoepithelial cells; e.g., p63, SMMHC)
• Excision is curative

• Uncommon
• Patient age > 60 years
• No family or personal history of breast cancer (Hum Pathol 1989;20:903)
• Ductal adenomas with tubular features occur as part of Carney complex (Am J Surg Pathol 1991;15:722, Am J Surg Pathol 1996;20:1154)

• Breast proliferative lesion genetically related to papilloma (Genes Chromosomes Cancer 2017;56:11)
• Similar to papilloma, AKT1 E17K mutations activate the PIK3CA pathway involved in cell proliferation, survival, angiogenesis and motility (Mod Pathol 2010;23:27)

• Presents as palpable lump or nipple discharge (less common) or mammographic abnormality (J Pathol 1984;144:15, Hum Pathol 1989;20:903)

• May resemble carcinoma on clinical examination, imaging, needle aspiration cytology and core biopsy (J Pathol 1984;144:15, Breast Cancer 2006;13:354)
• Excision is often recommended due to histological and radiological mimicry of carcinoma

• Imaging features may suggest papilloma, fibroadenoma or mimic carcinoma (Breast Cancer 2006;13:354)
• Mammography shows well to ill defined mass with or without calcification
• Ultrasonography shows a well defined, round hypoechoic nodule with shadowing and posterior enhancement
• On contrast enhanced MRI, margins are smooth despite histologic pseudoinvasion (Breast Cancer 2016;23:597)

Contributed by Thomas Lienhoop, M.D.

• Benign, with no increased risk for recurrence or malignant transformation after complete excision (Hum Pathol 1989;20:903)
• 1 case reported in the literature associated with malignant transformation to apocrine and epithelial myoepithelial carcinoma (Malays J Pathol 2015;37:281)

• Complete excision is curative (Hum Pathol 1989;20:903)

• Ranges in size from 0.5 to 5.0 cm (average: 0.85 cm) (J Pathol 1984;144:15)
• Solid white nodule with lobulated and granular cut surface and central gray softening
• Gritty texture and elastic streaks mimic carcinoma
• Solitary or occasionally multiple nodules in close proximity
• Multinodular tumors due to the involvement of different parts of the same ductal system (Hum Pathol 1989;20:903)

Contributed by Susanne M. Crespo-Ramos, M.D., Anna Biernacka, M.D., Ph.D. and AFIP

• Low Ki67 and p53 (Pathol Int 2008;58:801)

A 65 year old woman had a right breast lumpectomy showing a well circumscribed firm nodule with a lobulated and granular cut surface. Histologic features are shown in the image. Which of the following is the correct diagnosis?

1. Ductal adenoma
2. Fibroadenoma
3. Intraductal papilloma
4. Invasive ductal carcinoma
5. Tubular adenoma

A. Ductal adenoma. Ductal adenoma is a benign, well circumscribed adenomatous lesion in a duct surrounded by a densely thickened fibroelastotic wall. It has a solid architecture with an intermixture of tubules and sclerotic stroma and lacks arborizing papillary fronds. Answer C is incorrect because intraductal papillomas display arborizing papillary fronds. Answer D is incorrect because although gland distortion by sclerosis may mimic an infiltrative pattern, the myoepithelium is retained in this specimen. Answers B and E are incorrect because fibroadenomas and tubular adenomas arise from terminal duct lobular units rather than duct lumens and lack a prominent capsule. They are histogenetically related biphasic lesions, with the stromal component dominating fibroadenoma and florid adenosis-like epithelial proliferation dominating tubular adenoma.

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Reference: Ductal adenoma