A 48-year-old woman undergoes excisional biopsy of a 2.5 mm nodular melanoma on her forearm. Histology shows ulceration and 8 mitoses per mm². Which investigation is most appropriate for staging and prognostic stratification?

Explanation

## Staging Investigation for High-Risk Melanoma **Key Point:** Sentinel lymph node biopsy (SLNB) is the investigation of choice for staging melanomas with Breslow thickness ≥ 1 mm or high-risk features (ulceration, high mitotic rate ≥ 1/mm²), as it identifies occult nodal metastases and guides adjuvant therapy decisions. ### Indications for SLNB **High-Yield:** SLNB is recommended for: - Breslow thickness ≥ 1.0 mm (mandatory) - Breslow thickness 0.75–1.0 mm with adverse features (ulceration, high mitotic rate, young age) - Clark level IV–V with thickness < 1 mm ### Why SLNB in This Case? This patient has **multiple adverse prognostic factors**: 1. Breslow thickness 2.5 mm (stage IIB–IIC) 2. **Ulceration** (halves 5-year survival) 3. **High mitotic rate** 8/mm² (≥ 1/mm² is adverse) **Clinical Pearl:** Presence of ulceration alone upgrades stage by one level. Combined with high mitotic rate and thickness > 2 mm, this patient is at high risk for occult nodal disease (30–40% risk). ### SLNB Technique & Prognostic Value ```mermaid flowchart TD A[Melanoma with Breslow ≥ 1 mm or adverse features]:::outcome --> B[Perform SLNB]:::action B --> C{SLN positive?}:::decision C -->|Yes| D[Stage III: Regional nodal disease]:::outcome C -->|Yes| E[Consider adjuvant immunotherapy]:::action C -->|No| F[Stage IIB/IIC: No nodal involvement]:::outcome C -->|No| G[Observation or adjuvant therapy per AJCC]:::action ``` ### Staging Investigations — When Indicated | Investigation | Indication | Rationale | |---|---|---| | **SLNB** | Breslow ≥ 1 mm or high-risk features | Identifies occult nodal disease; guides adjuvant therapy | | **CT/MRI** | Stage III (nodal) or IV disease | Assess for distant metastases | | **Brain MRI** | Symptomatic or stage IV | High propensity for brain metastases | | **PET-CT** | Stage IV or high-risk stage III | Detect distant metastases; not routine for stage II | **Warning:** Routine imaging (CT, PET) is NOT recommended for asymptomatic stage I–II melanoma — low yield, high cost, and does not change management. **Mnemonic: SLNB Indications — "THICK & BAD"** - **T**hickness ≥ 1 mm - **H**igh mitotic rate (≥ 1/mm²) - **I**ntensity of ulceration - **C**lark level IV–V - **K** (prognostic factors) - **B**reslow ≥ 0.75 mm with adverse features - **A**ge < 40 years (relative) - **D**eep invasion [cite:Harrison 21e Ch 82; AJCC Cancer Staging Manual 8e]