Residency · Residency · Pathology
Breast Core Biopsy Interpretation: Benign and High-Risk Lesions
Introduction
Breast core needle biopsy (CNB) is the standard method for evaluating imaging-detected breast abnormalities. The pathologist must provide an accurate diagnosis and ensure radiologic-pathologic concordance. This lecture focuses on the spectrum of benign and high-risk lesions encountered in core biopsies and their management implications.
The Core Biopsy Workflow
Specimens arrive as cores (typically 3 to 6), often with a clip marker. All tissue should be submitted and sectioned at three levels with intervening unstained slides. The pathologist must correlate findings with the BI-RADS category and imaging modality. Discordant results require multidisciplinary discussion and possible re-biopsy or excision.
Benign Lesions
Fibrocystic Changes
Fibrocystic changes encompass cysts, apocrine metaplasia, stromal fibrosis, and mild ductal hyperplasia. They confer no increased cancer risk and are considered concordant with BI-RADS 2 to 3 calcifications.
Fibroadenoma
Fibroadenoma is a well-circumscribed biphasic lesion with both epithelial and stromal components. It may show intracanalicular or pericanalicular growth patterns. It is concordant with circumscribed masses on imaging.
Fat Necrosis
Fat necrosis is characterized by foamy histiocytes, foreign body giant cells, fibrosis, and calcifications. It often follows trauma or surgery and can mimic malignancy on imaging.
Usual Ductal Hyperplasia (UDH)
Usual ductal hyperplasia is a proliferative but benign process showing a streaming, swirling cell pattern with a heterogeneous cell population. CK5/6 is positive in a mosaic pattern, which is the key feature distinguishing it from atypical ductal hyperplasia (ADH).
High-Risk (B3) Lesions
| Lesion | Key Feature | Upgrade Rate to Carcinoma | Recommended Management |
|---|---|---|---|
| ADH | CK5/6-negative, <2 ducts or <2 mm | 15–30% | Excision |
| FEA | Columnar cell change with low-grade atypia | 5–15% | Excision or surveillance |
| ALH/Classic LCIS | E-cadherin loss | 5–10% | Excision vs. surveillance (debated) |
| Pleomorphic LCIS | E-cadherin loss, high-grade nuclei | Higher | Excision |
| Radial scar | Stellate architecture, central fibroelastosis | Variable | Excision |
| Atypical papilloma | Papilloma with ADH/DCIS | Higher | Excision |
Atypical Ductal Hyperplasia (ADH)
ADH resembles low-grade DCIS but involves fewer than two completely involved duct spaces or measures less than 2 mm. The atypical cell population is CK5/6-negative, in contrast to the mosaic pattern of UDH. The upgrade rate to carcinoma at excision is 15 to 30 percent, and excision is recommended in most clinical scenarios.
Flat Epithelial Atypia (FEA)
FEA represents columnar cell change with low-grade cytologic atypia in one to several cell layers. It is often associated with amorphous calcifications. The upgrade rate is 5 to 15 percent, and management is evolving toward surveillance in some centers rather than mandatory excision.
Lobular Neoplasia
Lobular neoplasia includes atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS). Loss of E-cadherin expression is the diagnostic hallmark. Classic LCIS carries an upgrade rate of approximately 5 to 10 percent, and the choice between excision and surveillance is debated. Pleomorphic LCIS has a higher upgrade rate and excision is recommended.
Radial Scar / Complex Sclerosing Lesion
Radial scar has a stellate architecture with central fibroelastosis. It mimics invasive carcinoma on both imaging and histology. Associated atypia or carcinoma must be excluded, and excision is often recommended.
Papillary Lesions
Intraductal papilloma is characterized by a fibrovascular core with an intact myoepithelial cell layer. Atypical papillomas (containing ADH or DCIS) carry a higher upgrade rate. Myoepithelial markers (p63, CK5/6, calponin) help assess the integrity of the myoepithelial layer and distinguish benign from malignant papillary lesions.
Radiologic-Pathologic Concordance
The pathologist must assess whether the histologic findings explain the imaging abnormality. A concordant result would be a fibroadenoma on core matching a circumscribed mass on imaging. A discordant result would be benign breast tissue on core for a BI-RADS 5 spiculated mass. Discordance requires re-biopsy, excision, or multidisciplinary review.
Reporting Considerations
Reports should use standardized terminology aligned with institutional practice. They must include lesion type, presence of calcifications in the specimen, and a concordance assessment. Excision should be clearly recommended when indicated for high-risk lesions. The pathologist should note if additional levels, immunohistochemistry, or re-biopsy is warranted.
Clinical Pearls
ADH on core biopsy requires excision because a significant minority of cases will be upgraded to DCIS or invasive carcinoma on the excision specimen. E-cadherin immunohistochemistry is essential for distinguishing lobular from ductal proliferations, as this distinction impacts both risk stratification and surgical planning. The pathologist should always verify that calcifications seen on imaging are present in the histologic sections and request specimen radiography correlation when needed. Discordant results represent a critical safety net in the diagnostic process and must be communicated to the clinical team promptly.
References
- Pinder SE, et al. Non-operative breast pathology: columnar cell lesions. J Clin Pathol. 2007;60(12):1307-1312.
- Rageth CJ, et al. Second International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions). Breast Cancer Res Treat. 2019;174(2):279-296.
- Hartmann LC, et al. Atypical hyperplasia of the breast—risk assessment and management options. N Engl J Med. 2015;372(1):78-89.
- NHS Breast Screening Programme. Guidelines for Non-Operative Diagnostic Procedures and Reporting in Breast Cancer Screening. Publication No 58. 2016.