A 52-year-old man from Delhi presents with a 6-month history of a pigmented lesion on his left shoulder. On examination, the lesion measures 8 mm in diameter with irregular borders, color variegation (brown, black, and red), and mild surface ulceration. Dermoscopy shows asymmetry, atypical network pattern, and blue-white veil. Excision biopsy confirms melanoma with a Breslow thickness of 2.4 mm, 3 mitoses per mm², and no ulceration on histology. Sentinel lymph node biopsy is negative. What is the AJCC TNM stage of this melanoma?

Explanation

## AJCC TNM Staging for Melanoma (8th Edition) **Key Point:** Melanoma staging integrates Breslow thickness, mitotic rate, and ulceration status for T-staging, combined with N-stage (lymph node involvement) and M-stage (distant metastasis). ### T-Stage Classification | T-Stage | Breslow Thickness | Ulceration | Mitotic Rate | |---------|-------------------|------------|---------------| | T1 | ≤1.0 mm | Without ulceration | Any | | T1a | ≤0.8 mm | Without ulceration | — | | T1b | ≤1.0 mm | With ulceration OR mitotic rate ≥1/mm² | — | | T2 | 1.01–2.0 mm | — | — | | T2a | 1.01–2.0 mm | Without ulceration | — | | T2b | 1.01–2.0 mm | With ulceration | — | | T3 | 2.01–4.0 mm | — | — | | T3a | 2.01–4.0 mm | Without ulceration | — | | T3b | 2.01–4.0 mm | With ulceration | — | | T4 | >4.0 mm | — | — | ### Analysis of This Case **Breslow thickness:** 2.4 mm → **T3a** (2.01–4.0 mm without ulceration; histology shows no ulceration despite surface ulceration on exam) **Lymph node status:** Sentinel lymph node biopsy negative → **N0** **Distant metastasis:** No mention → **M0** ### Stage Determination (AJCC 8th Edition) ```mermaid flowchart TD A[Breslow 2.4 mm, no ulceration, mitotic rate 3/mm²]:::outcome --> B[T3a classification]:::outcome C[Negative SLN biopsy]:::outcome --> D[N0 classification]:::outcome E[No distant metastasis]:::outcome --> F[M0 classification]:::outcome B --> G[T3a N0 M0]:::outcome D --> G F --> G G --> H{Stage?}:::decision H -->|T3a N0 M0| I[Stage IIB]:::action ``` **Stage IIB** corresponds to T3a N0 M0 (Breslow 2.01–4.0 mm without ulceration, node-negative). **High-Yield:** The presence of mitotic rate ≥1/mm² does NOT upgrade T1 lesions to T1b if ulceration is absent; however, in T2–T4 lesions, mitotic rate is NOT a T-stage modifier — only Breslow thickness and ulceration matter. This patient's 3 mitoses/mm² does not change T-staging but would have been critical if Breslow were ≤1.0 mm. **Clinical Pearl:** Sentinel lymph node biopsy is recommended for melanomas ≥1 mm thick or with high-risk features (ulceration, high mitotic rate). Negative SLN keeps the patient at Stage II rather than Stage III. **Mnemonic: "SLNB Saves Stage"** — Negative sentinel lymph node biopsy prevents upstaging to Stage III (regional nodal disease).