A 52-year-old man from Bangalore presents with a 6-month history of a pigmented lesion on his left shoulder. On examination, there is an irregularly bordered, asymmetrical dark brown macule measuring 8 mm with colour variegation (brown, black, and tan). Dermoscopy shows asymmetrical pigment network with irregular streaks. An excisional biopsy confirms cutaneous melanoma with Breslow thickness of 2.8 mm, Clark level IV, and no ulceration. Sentinel lymph node biopsy is negative. There are no distant metastases on staging imaging. What is the AJCC TNM stage of this melanoma?

Explanation

## AJCC TNM Staging for Cutaneous Melanoma (8th Edition) **Key Point:** The AJCC 8th edition staging system for melanoma uses Breslow thickness (in mm), ulceration status, and mitotic rate for T staging; nodal involvement for N staging; and distant metastases for M staging. ### T-Stage Determination | Breslow Thickness | Ulceration | Mitotic Rate | T-Stage | |---|---|---|---| | ≤0.8 mm | No | Any | T1a | | ≤0.8 mm | Yes | Any | T1b | | 0.81–1.0 mm | No | Any | T1b | | 0.81–1.0 mm | Yes | Any | T2a | | 1.01–2.0 mm | No | Any | T2a | | 1.01–2.0 mm | Yes | Any | T2b | | 2.01–4.0 mm | No | Any | T3a | | 2.01–4.0 mm | Yes | Any | T3b | | >4.0 mm | No | Any | T4a | | >4.0 mm | Yes | Any | T4b | ### Analysis of This Case - **Breslow thickness:** 2.8 mm (falls in 2.01–4.0 mm range) - **Ulceration:** Absent (no) - **T-Stage:** T3a (2.01–4.0 mm, no ulceration) - **N-Stage:** N0 (sentinel lymph node biopsy negative) - **M-Stage:** M0 (no distant metastases) ### Stage Grouping | T-Stage | N-Stage | M-Stage | Clinical Stage | |---|---|---|---| | T3a | N0 | M0 | **IIB** | **High-Yield:** Breslow thickness >2 mm is considered "thick" melanoma and carries significantly higher risk of nodal and systemic recurrence. Stage IIB represents locally advanced disease without nodal involvement—these patients require close surveillance and consideration of adjuvant therapy (interferon-α or checkpoint inhibitors). **Clinical Pearl:** Clark level is no longer used in AJCC 8th edition staging but remains prognostically relevant. Mitotic rate was important in AJCC 7th edition but has been de-emphasized in the 8th edition in favour of Breslow thickness and ulceration. **Mnemonic:** **BUNT** = **B**reslow thickness, **U**lceration, **N**odal involvement, **T**umour metastases—the four pillars of melanoma staging. [cite:AJCC Cancer Staging Manual 8th Edition, Cutaneous Melanoma]