Role of Core Needle Biopsy in Breast Pathology

1. Overview and Why CNB is Preferred

• Less invasive and less expensive than excisional biopsy
• Performed under local anaesthesia as an outpatient procedure
• Able to preserve tissue architecture - enabling histological (not just cytological) diagnosis
• Able to discriminate between invasive and non-invasive breast cancer (a distinction FNA cannot reliably make)
• Capable of providing sufficient material for ancillary biomarker testing (ER, PR, HER2, Ki-67)

2. CNB vs Fine-Needle Aspiration (FNA)

3. Technical Aspects of CNB

Needle Size and Device

• Standard CNB uses 14-gauge needles for breast tissue and 18-gauge for axillary lymph nodes
• Spring-loaded automated devices are standard
• Vacuum-assisted biopsy (VAB) uses 7-12 gauge needles (9G most popular), allowing multiple samples (up to 12) with a single insertion, rotating 360° around the lesion

Image Guidance - Always Required

1. Ultrasound-guided CNB - first choice for most breast lesions; avoids radiation, real-time needle visualization; used for palpable and non-palpable masses
2. Stereotactic (mammography-guided) CNB - used for non-palpable lesions visible only on mammogram, especially microcalcifications. Uses triangulation to localize the lesion in 3D. Patient is prone on a dedicated table.
3. MRI-guided CNB - reserved for lesions visible only on MRI

Specimen Imaging

4. Role in Diagnosis of Specific Breast Lesions

Benign/Non-Proliferative Lesions (No increased cancer risk)

• Usual ductal hyperplasia (UDH), simple cysts, fibroadenoma
• CNB establishes the benign diagnosis; if concordant with imaging, no surgical excision needed
• Return to routine surveillance

Proliferative Disease Without Atypia (~2x relative risk)

• Moderate/florid ductal hyperplasia, sclerosing adenosis, radial scar, solitary papilloma, papillomatosis
• CNB establishes the diagnosis; management depends on radiologic-pathologic concordance
• Radial scar on CNB: surgical excision recommended due to upgrade risk

High-Risk (Atypical) Lesions (>2x relative risk - Upgrade Risk on Excision)

Malignant Lesions

• Definitive diagnosis of invasive vs. in situ carcinoma (DCIS)
• Histological grade (Nottingham grading)
• Biomarker assessment: ER, PR, HER2 (IHC ± FISH), and Ki-67 proliferation index
• Molecular subtyping guiding neoadjuvant vs. adjuvant therapy decisions

5. Radiologic-Pathologic Concordance

• Concordant result: imaging differential matches pathology - patient can return to surveillance or proceed per risk category
• Discordant result (e.g., BI-RADS 5 lesion with benign histology): concern that the target was missed or undersampled; surgical excision is mandatory

6. Vacuum-Assisted Biopsy (VAB) - Enhanced CNB

• Larger tissue volume per pass (9G device removes up to ~1 cm of tissue)
• Multiple harvests in 360° with single insertion
• Significantly lower false-negative rate for microcalcifications: repeat biopsy rate 11.6% vs 23.7% for standard CNB
• Superior for DCIS: only 6% upgraded to invasive carcinoma at surgery after VAB vs 21% with 14G CNB
• Near 3x more accurate than standard CNB for ADH, though underestimation still occurs in 18-25% of ADH cases
• Can remove entire small lesions percutaneously (useful for small fibroadenomas)
• Standard approach for stereotactic biopsy of microcalcifications

7. Indications for Surgical Excision After CNB

1. Atypical ductal hyperplasia (ADH) on CNB
2. Radial scar
3. Columnar cell hyperplasia with atypia
4. Papillary lesions
5. Lack of concordance between mammographic appearance and histologic diagnosis
6. Nondiagnostic specimen (e.g., absent calcifications on specimen radiograph when biopsy done for calcifications)
7. LCIS in certain settings

8. Limitations and Pitfalls of CNB

• Sampling error (false-negative): rare but possible; the false-negative rate is low but not zero. Vacuum-assisted devices reduce this substantially
• Underestimation ("upgrade" phenomenon): especially for ADH (upgraded to DCIS or invasive cancer in 5-25% at excision) and DCIS (upgraded to invasive cancer in ~20% at final surgical pathology)
• Non-diagnostic specimens: inadequate cores, absence of target tissue (calcifications missing from specimen)
• Technical limitations: very small breasts, deep posterior lesions, anticoagulated patients, pregnancy (for stereotactic approach), or inability to tolerate positioning

Summary

• Mulholland and Greenfield's Surgery, 7th ed. - Breast Surgery chapter
• Fischer's Mastery of Surgery, 8th ed. - Benign Breast Lesions and CNB Concordance
• Bailey and Love's Short Practice of Surgery, 28th ed. - Breast chapter
• Current Surgical Therapy, 14th ed. - Stereotactic Biopsy and Equipment
• Harrison's Principles of Internal Medicine, 22nd ed. (2025) - Breast Cancer Diagnosis and Staging
• Sharma N et al. (2026). Vacuum-assisted breast biopsy vs core needle biopsy: a systematic review and meta-analysis. Eur Radiol [PMID: 41553473]

Borderline Breast Lesions (B3 Lesions) - SAQ

Definition

Classification of Breast Epithelial Lesions by Cancer Risk

B3 Lesions: Individual Entities

1. Flat Epithelial Atypia (FEA)

• Pathology: A columnar cell lesion (CCL) with low-grade cytologic atypia but absence of architectural complexity. Cells are cuboidal-to-columnar with round, monomorphic, hyperchromatic, uniform nuclei and no prominent nucleoli. TDLUs are enlarged with dilated acini containing inspissated/calcified secretions.
• Considered the earliest morphologically recognizable precursor in the low-grade breast neoplasia pathway
• Expresses high levels of ER; low proliferation rate
• Often presents as microcalcifications on mammography (incidental finding)
• Upgrade risk to cancer on excision: ~5% (for pure FEA)
• Long-term relative risk: 2.0x
• Management: Observation (no excision) if: large-bore needle used (≤14G), adequately sampled, radiologic-pathologic concordance. National guidelines (NCCN) support nonsurgical management. Caveat: know your institutional upgrade rates.

2. Atypical Ductal Hyperplasia (ADH)

• Pathology: A monomorphic epithelial proliferation of the TDLU showing both cytologic atypia AND architectural changes resembling low-grade DCIS - but limited in extent and/or smaller in size. Cribriform or micropapillary patterns may be present.
• Distinguished from DCIS by: limited extent (less than 2 full duct spaces or <2 mm)
• Present in approximately 10% of biopsies performed to evaluate calcifications

• Upgrade risk to DCIS/invasive carcinoma on excision: 10-20% (some literature 5-25%)
• Long-term relative risk: 4x general population; increases to 11-20x with family history of breast cancer
• Absolute risk: 1-2% per year (higher if >3 foci)
• Note: Standard Gail model and Tyrer-Cuzick do NOT accurately predict risk in the setting of ADH
• Management: Surgical excision is the standard recommendation UNLESS ALL of the following low-risk criteria are met:
  • Large-bore needle used (<14G)

  • 90% of the determinant calcifications removed (adequately sampled)

  • Radiologic-pathologic concordance
  • ≤2 foci of ADH
  • No cell necrosis
  • No mass lesion or discordance
• If observation is selected after meeting criteria: high-risk surveillance (annual mammography + annual breast MRI or whole-breast ultrasound) + chemoprevention

3. Atypical Lobular Hyperplasia (ALH)

• Pathology: Neoplastic proliferation of dyscohesive cells confined to the ductal-lobular system - histologically identical to classic LCIS but less extensive. The lobular unit must be filled with <50% of these cells, without significant distortion.
• Cells are uniform, round, loosely cohesive - pathognomonic appearance
• Shows loss of E-cadherin expression (shared feature with LCIS and invasive lobular carcinoma)
• Usually an incidental finding (not associated with specific imaging findings; calcifications may be present incidentally)
• Upgrade risk to cancer on excision: 1-4% (comparable to BI-RADS 3)
• Long-term relative risk: 3-5x general population
• Management: Observation (no excision needed) IF: incidental finding, radiologic-pathologic concordance, large-bore needle, adequately sampled, and target lesion itself does not require excision. If excised, no negative margin required.
• High-risk surveillance + chemoprevention recommended

4. Lobular Carcinoma In Situ (LCIS) - Classic Type

• Pathology: More extensive than ALH - characteristic lobular neoplasia cells distend and efface >50% of lobular acini, with significant distortion. Loss of E-cadherin is characteristic.
• A nonobligate precursor to invasive carcinoma AND a risk marker for both breasts
• Removed from the 8th edition AJCC staging system; now classified as "lobular neoplasia"
• Upgrade risk on excision: <5% when concordant and adequately sampled (no excision needed)
• Long-term relative risk: 6-10x general population; 1-2% per year
• Cumulative risk (SEER data): 11.3% at 10 years, 19.8% at 20 years
• Management: Observation if concordant (a-e criteria same as ALH above). High-risk surveillance + chemoprevention are the emphasis.
• Exception - Pleomorphic LCIS: higher-grade variant; treated more like DCIS with surgical excision

5. Radial Scar / Complex Sclerosing Lesion

• Pathology: Originates at the point of terminal duct branching. Contains a firm central fibroelastic core with elastic streaks, entrapped small tubules in fibrotic stroma, and projections containing epithelium with variable cyst formation/hyperplasia. An intact myoepithelial layer is always present. By definition, a radial scar is ≤10 mm (larger lesions = complex sclerosing lesion).
• Easily confused with malignancy on mammography - both create spiculated patterns. Distinguishing feature: the center of a radial scar is hollow ("black star/black hole"), while carcinoma has a solid central mass.

• Upgrade risk on excision: ≤3% (low), provided: large-bore needle (≤14G), adequately sampled, size ≤10 mm, radiologic-pathologic concordance
• If discordance or associated atypia: upgrade rate rises to 26-40% - excision mandatory
• Long-term relative risk: 1.82-2.63x at 10 years; ~7% risk of breast cancer at 20 years
• Management: Observation vs. excision - multidisciplinary decision based on above criteria. Annual breast exam and mammography if observed; excise if growth/suspicious change develops.
• Incidentally found on 2-28% of benign breast biopsies

6. Papillary Lesions

• Solitary (central) intraductal papilloma: Arises in major sub-areolar ducts. Fibrovascular core lined by both myoepithelial and luminal cells. Presents with bloody/serous nipple discharge.
  • Upgrade risk averages 5-10% in modern datasets
  • If adequately sampled and concordant - observation may be selected for small lesions
  • Surgical excision if discordant, if >10 mm, associated with atypia, or if growth on follow-up
• Peripheral papillomatosis (multiple papillomas): Located in terminal ductal lobular units; higher upgrade risk than solitary papilloma
  • Surgical excision recommended for peripheral papillomatosis with discordance
• Atypical papilloma (papilloma involved by ADH, ALH, or LCIS):
  • Upgrade rate to carcinoma: 10-38% (wide range)
  • Surgical excision is mandatory
  • If excision shows no cancer, long-term relative risk is 5.1-13.1x - high-risk surveillance + chemoprevention required

Summary Table: Management of B3 Lesions

The Upgrade Concept - Key SAQ Point

1. Concurrent cancer risk (upgrade risk): Risk that cancer is present in adjacent breast tissue at the biopsy site RIGHT NOW - determined by surgical excision
2. Future cancer development risk: Risk of developing breast cancer in either breast over the next 20 years - managed by high-risk surveillance and chemoprevention

Role of Multidisciplinary Team (MDT)

• Was a large-bore needle used (≤14G)?
• Was the lesion adequately sampled?
• Is there radiologic-pathologic concordance?

Chemoprevention (Risk Reduction) for B3 Lesions

• Endocrine therapy: Tamoxifen, raloxifene, anastrozole, or exemestane - taken daily for 5 years
• Reduces breast cancer risk by ~50% overall
• Combined with high-risk surveillance: clinical breast exam every 6 months + annual mammography + annual breast MRI (or whole-breast ultrasound)
• Lifestyle: maintain healthy weight, limit alcohol, moderate exercise ≥150 min/week

• Robbins, Cotran & Kumar Pathologic Basis of Disease - Table 23.1 and Proliferative Breast Disease with Atypia
• Fischer's Mastery of Surgery, 8th ed. - Benign Breast Lesions: Histopathology, Management after CNB
• Current Surgical Therapy, 14th ed. - Proliferative Lesions with and without Atypia
• Mulholland and Greenfield's Surgery, 7th ed. - Breast chapter (Key Points)
• Grainger & Allison's Diagnostic Radiology - VAB and B3 Lesions