A 52-year-old woman presents with a palpable hard mass in the upper outer quadrant of the left breast. Clinical examination reveals skin dimpling and a single ipsilateral axillary lymph node. Mammography shows a 2 cm irregular density with microcalcifications. What is the most appropriate next investigation to confirm the diagnosis?

Explanation

## Diagnostic Approach to Breast Masses **Key Point:** Core needle biopsy (CNB) is the gold standard for histological diagnosis of suspicious breast lesions identified on imaging. ### Why CNB is the Investigation of Choice CNB offers several advantages in the diagnostic algorithm: 1. **Tissue diagnosis** — provides histological confirmation, essential before any treatment planning 2. **Minimally invasive** — outpatient procedure with low morbidity 3. **High diagnostic accuracy** — sensitivity and specificity >95% for malignancy [cite:Robbins 10e Ch 24] 4. **Cost-effective** — cheaper than excisional biopsy, avoids unnecessary surgery 5. **Image-guided** — can be performed under ultrasound or stereotactic guidance for non-palpable lesions ### Diagnostic Algorithm for Breast Lesions ```mermaid flowchart TD A[Palpable breast mass + imaging abnormality]:::outcome --> B{Imaging findings suggestive of malignancy?}:::decision B -->|Yes| C[Core needle biopsy]:::action B -->|No| D[Follow-up imaging] C --> E{Malignancy confirmed?}:::decision E -->|Yes| F[Staging investigations + treatment planning]:::action E -->|No| G[Clinical follow-up] ``` ### Comparison of Biopsy Methods | Biopsy Method | Tissue Yield | Invasiveness | Cost | Indications | |---|---|---|---|---| | **Core Needle (CNB)** | Excellent | Minimally invasive | Low | First-line for suspicious lesions | | **Fine Needle Aspiration (FNA)** | Limited cells | Least invasive | Very low | Cystic lesions, lymph nodes | | **Excisional Biopsy** | Complete lesion | Surgical | High | Diagnostic uncertainty, therapeutic | | **Vacuum-Assisted Biopsy** | Large samples | Minimally invasive | Moderate | High-risk lesions, papillomas | **High-Yield:** In this case, the imaging findings (irregular density with microcalcifications) and clinical signs (skin dimpling, axillary lymphadenopathy) are highly suspicious for malignancy — CNB is mandatory for tissue diagnosis before any staging or treatment. **Clinical Pearl:** The presence of skin dimpling and axillary lymphadenopathy suggests advanced local disease; however, histological confirmation remains the essential first step before staging investigations like CT or PET-CT are ordered.