A 52-year-old man presents with a pigmented lesion on his back that has been present for 15 years but has recently shown rapid growth and color change. Dermoscopy reveals asymmetry, irregular borders, and mixed colors. Which investigation is most appropriate to confirm the diagnosis of melanoma and assess its prognostic significance?

## Investigation of Choice for Melanoma Diagnosis ### Role of Excisional Biopsy **Key Point:** Excisional biopsy with full-thickness histopathological examination is the gold standard for diagnosing melanoma and determining critical prognostic factors. ### Why Histopathology is Essential Histopathological examination provides: 1. **Definitive diagnosis** — Confirms melanoma vs. benign nevus 2. **Breslow thickness** — Most important prognostic factor; measured in millimeters from granular layer to deepest tumor cell 3. **Clark level** — Depth of invasion relative to skin layers (I–V) 4. **Ulceration** — Present/absent; worsens prognosis significantly 5. **Mitotic rate** — Number of mitoses per mm²; high rate indicates poor prognosis 6. **Margin assessment** — Ensures adequate clearance 7. **Lymphovascular invasion** — Predicts nodal metastasis risk **High-Yield:** Breslow thickness >4 mm, presence of ulceration, and high mitotic rate (≥1/mm²) are the three strongest independent prognostic factors in melanoma. ### Excisional vs. Incisional Biopsy | Feature | Excisional | Incisional | |---------|-----------|----------| | **Recommended for** | All suspicious pigmented lesions | Large lesions where excision not feasible | | **Margin clearance** | Assessed | Not assessed | | **Breslow thickness** | Accurate | May be underestimated | | **Staging accuracy** | Complete | Incomplete | **Clinical Pearl:** Incisional or punch biopsy should be avoided for suspected melanoma because sampling error may miss the deepest (thickest) portion, leading to understaging. ### Timing of Staging Investigations Once melanoma is confirmed histologically: - **Stage I–II (Breslow ≤4 mm, no ulceration):** Clinical examination + optional sentinel lymph node biopsy - **Stage III (nodal involvement):** Sentinel lymph node biopsy - **Stage IV (metastatic):** CT chest/abdomen/pelvis ± PET-CT **Mnemonic:** **BUMP** — **B**reslow thickness, **U**lceration, **M**itotic rate, **P**rognostic factors all determined by histopathology.