## Prognostic Factors in Melanoma **Key Point:** Breslow thickness (depth in millimeters) is the single most important prognostic factor in melanoma, not Clark level alone. Clark level has been largely superseded in modern staging. ### Well-Established Prognostic Factors | Factor | Significance | Impact on Prognosis | |--------|--------------|--------------------| | **Breslow thickness** | Depth in mm from granular layer to deepest tumor cell | Most important; directly correlates with survival | | **Mitotic rate** | ≥1 mitosis/mm² is adverse | Independent predictor of poor prognosis | | **Ulceration** | Presence indicates aggressive behavior | Worsens prognosis at any thickness | | **Regression** | Presence of fibrosis/inflammation replacing tumor | May indicate immune response; controversial prognostic value | | **Clark level** | Anatomical depth (I–V) | Outdated; replaced by Breslow thickness in AJCC staging | **High-Yield:** The 2016 AJCC melanoma staging system emphasizes: 1. Breslow thickness (primary determinant) 2. Mitotic rate (for T1 lesions) 3. Ulceration (upstages by one level) 4. Clark level is NO LONGER used for staging **Clinical Pearl:** Clark level was historically used but is now considered less precise than Breslow thickness. A thin melanoma (Breslow <1 mm) with high mitotic rate may have worse prognosis than a thicker lesion with low mitotic rate. ### Why Clark Level Alone Is Insufficient - Clark level describes anatomical layers (dermis, subcutis) but does NOT quantify actual depth - Two lesions at the same Clark level can have vastly different Breslow thicknesses - Modern prognostication relies on **Breslow thickness** as the primary metric - Clark level is retained only for historical reference and certain research contexts **Warning:** Do not confuse Clark level with Breslow thickness. Clark = layers; Breslow = millimeters. The latter is prognostically superior. [cite:Robbins 10e Ch 25]
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