According to the AJCC 8th edition staging system for cutaneous melanoma, which of the following is the PRIMARY determinant of T stage?

Explanation

## AJCC 8th Edition T Staging for Melanoma **Key Point:** Breslow thickness (measured in millimeters from the granular layer to the deepest tumor cell) is the MOST important prognostic factor and PRIMARY determinant of T stage in cutaneous melanoma. ### T Stage Criteria | T Stage | Breslow Thickness | Ulceration | Mitotic Rate | |---------|-------------------|-----------|---------------| | T1 | ≤1.0 mm | Without ulceration = 1a; With ulceration = 1b | — | | T2 | 1.01–2.0 mm | Without ulceration = 2a; With ulceration = 2b | — | | T3 | 2.01–4.0 mm | Without ulceration = 3a; With ulceration = 3b | — | | T4 | >4.0 mm | Without ulceration = 4a; With ulceration = 4b | — | **High-Yield:** Ulceration is a secondary modifier that upstages within the same thickness category (e.g., T1a → T1b). Mitotic rate is NO LONGER used for T staging in AJCC 8e. ### Historical Context **Warning:** Clark level (I–V) was the primary staging criterion in older systems but is now only used when Breslow thickness cannot be measured. Do NOT confuse Clark level with current AJCC T staging. **Clinical Pearl:** A melanoma 1.5 mm thick WITHOUT ulceration = T2a; the SAME thickness WITH ulceration = T2b — ulceration worsens prognosis within the same thickness group. [cite:AJCC Cancer Staging Manual 8th Edition, Melanoma of the Skin]