A 68-year-old woman from Mumbai presents with a 10-month history of a dark nodular lesion on her right calf. She reports that the lesion has grown rapidly and recently started bleeding. On examination, the lesion is 12 mm in diameter, deeply pigmented, with a dome-shaped appearance and surface bleeding. Histopathology reveals melanoma with a Breslow thickness of 3.8 mm, ulceration present, and 8 mitoses per mm². Imaging (CT chest/abdomen/pelvis and brain MRI) shows no evidence of distant metastasis. Sentinel lymph node biopsy reveals metastatic melanoma in 2 of 3 sentinel nodes. What is the AJCC TNM stage?

Explanation

## AJCC TNM Staging for Melanoma with Regional Nodal Disease **Key Point:** When sentinel lymph node biopsy is positive, the patient is upstaged to Stage III (regional nodal disease). The number of involved nodes and tumor burden in nodes determine the N-stage and overall stage. ### T-Stage Assessment **Breslow thickness:** 3.8 mm → **T3b** (2.01–4.0 mm WITH ulceration) Ulceration is present on histology, which is the critical T-stage modifier for lesions 2.01–4.0 mm. ### N-Stage Assessment **Sentinel lymph node involvement:** 2 of 3 nodes positive → **N2a** (2–3 nodes involved, micrometastasis or macrometastasis) | N-Stage | Number of Nodes | Tumor Burden | |---------|-----------------|---------------| | N0 | 0 nodes | — | | N1a | 1 node | Micrometastasis | | N1b | 1 node | Macrometastasis | | N2a | 2–3 nodes | Micrometastasis | | N2b | 2–3 nodes | Macrometastasis | | N2c | 1 node | Macrometastasis | | N3a | ≥4 nodes OR any nodes with matted nodes OR in-transit metastasis with nodal involvement | — | | N3b | ≥4 nodes OR matted nodes OR in-transit + nodal disease | — | | N3c | In-transit metastasis/satellites with nodal disease | — | ### M-Stage Assessment **Imaging:** CT and brain MRI negative for distant metastasis → **M0** ### Overall Stage Determination ```mermaid flowchart TD A[Breslow 3.8 mm + Ulceration]:::outcome --> B[T3b]:::outcome C[2 of 3 SLN positive]:::outcome --> D[N2a]:::outcome E[No distant metastasis]:::outcome --> F[M0]:::outcome B --> G[T3b N2a M0]:::outcome D --> G F --> G G --> H{AJCC Stage?}:::decision H -->|T3b N2a M0| I[Stage IIIC]:::action ``` **Stage IIIC** corresponds to T3b N2a M0 (thick ulcerated melanoma with 2–3 positive nodes). ### Stage III Substratification (AJCC 8th Edition) | Stage | T-Stage | N-Stage | M-Stage | |-------|---------|---------|----------| | IIIA | T1–T4 | N1a | M0 | | IIIA | T1–T4 | N2a | M0 | | IIIB | T1–T4 | N1b | M0 | | IIIB | T1–T4 | N2b | M0 | | IIIB | T1–T4 | N2c | M0 | | IIIC | T1–T4 | N3a, N3b, N3c | M0 | | IIIC | T1–T4 | Any N ≥1 | M0 (if macrometastasis) | **High-Yield:** Positive sentinel lymph nodes automatically place the patient in Stage III. The specific substage (IIIA, IIIB, or IIIC) depends on the number of involved nodes and whether metastases are micrometastases (found only on SLN biopsy) or macrometastases (clinically evident or >0.1 mm on histology). Two positive nodes with macrometastatic disease = N2b, but if the question states "metastatic melanoma" in nodes without specifying size, assume macrometastasis → N2b → Stage IIIB. However, the question states "metastatic melanoma in 2 of 3 sentinel nodes," which typically implies macrometastasis, but the standard classification for 2–3 nodes is N2 (either N2a or N2b). Given the clinical presentation (rapid growth, ulceration, high mitotic rate), assume macrometastasis → N2b → Stage IIIB. **Correction:** Re-reading the AJCC 8th edition, N2a = 2–3 nodes with micrometastasis, N2b = 2–3 nodes with macrometastasis. Since the question does not specify micrometastasis, and SLN biopsy typically detects macrometastases, this is N2b → Stage IIIB. However, if the question intends N2a (micrometastasis), the answer would be Stage IIIA. The most conservative interpretation: 2 positive nodes = N2 (either a or b), and with T3b, the stage is at least IIIB. **Final answer: Stage IIIB** (T3b N2b M0). **Clinical Pearl:** Patients with Stage IIIB–IIIC melanoma are candidates for adjuvant immunotherapy (nivolumab, pembrolizumab, or combination ipilimumab + nivolumab) based on recent trials (CheckMate 238, KEYNOTE-054). **Mnemonic: "SLN Positive = Stage III"** — Any positive sentinel lymph node automatically places the patient in Stage III regional disease, regardless of T-stage.