A 52-year-old woman from Delhi presents with a 2 cm palpable mass in the upper outer quadrant of the left breast. Clinical examination reveals a single ipsilateral axillary lymph node (1.5 cm, mobile, firm). Mammography and ultrasound confirm a suspicious lesion. Core needle biopsy shows invasive ductal carcinoma, grade II. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient has a clinically node-positive (cN1) breast cancer with a palpable axillary lymph node. Before committing to a surgical plan, complete staging and molecular profiling are essential to guide optimal treatment. ## Why Staging Investigations Are Mandatory **Key Point:** In patients with clinical evidence of axillary involvement or tumours ≥2 cm, staging investigations (chest X-ray, abdominal ultrasound, bone scan or PET-CT) are required to exclude distant metastases before surgery. **High-Yield:** The TNM staging system mandates: - **T stage**: Tumour size (2 cm = T1c or T2 depending on exact measurement) - **N stage**: Lymph node involvement (palpable axillary node = cN1) - **M stage**: Metastatic disease (must be ruled out) ## Molecular Profiling **Clinical Pearl:** ER/PR and HER2 status determine: - Eligibility for hormone therapy (ER/PR+) - Indication for anti-HER2 therapy (HER2+) - Chemotherapy regimen selection These results directly influence whether neoadjuvant therapy is indicated before surgery. ## Decision Algorithm ```mermaid flowchart TD A[Invasive breast cancer diagnosed on biopsy]:::outcome --> B{Complete staging done?}:::decision B -->|No| C[Chest X-ray, Abdominal ultrasound, Bone scan/PET-CT]:::action B -->|Yes| D[Assess ER/PR/HER2 status]:::action C --> D D --> E{Distant metastases?}:::decision E -->|Yes| F[Palliative therapy]:::outcome E -->|No| G{Node-positive or high-risk?}:::decision G -->|Yes| H[Consider neoadjuvant chemotherapy]:::action G -->|No| I[Proceed to surgery]:::action ``` ## Why This Approach 1. **Staging first** prevents unnecessary surgery in metastatic disease 2. **Molecular profiling** personalizes treatment (chemotherapy, hormone therapy, anti-HER2 agents) 3. **Neoadjuvant therapy** may be indicated in node-positive disease to downstage and improve breast conservation candidacy **Mnemonic:** **STAMP** — **S**taging, **T**umour biology (molecular), **A**ssess metastases, **M**anage optimally, **P**roceed to surgery [cite:Harrison 21e Ch 297]