## Diagnosis: Nodular Melanoma ### Clinical Presentation **Key Point:** Nodular melanoma (NM) is characterized by a vertical growth phase from onset, with dermal invasion and minimal or absent intraepidermal component. ### Histopathological Features - Predominantly dermal lesion with nests of melanoma cells - Lack of significant radial growth phase (RGP) - Vertical growth phase (VGP) is the defining feature - No prominent epidermal involvement ### Distinguishing Features of Melanoma Subtypes | Feature | Nodular | Superficial Spreading | Lentigo Maligna | Acral Lentiginous | |---------|---------|----------------------|-----------------|-------------------| | **Growth Phase** | Vertical from onset | RGP then VGP | Prolonged RGP | RGP then VGP | | **Epidermal Involvement** | Minimal | Prominent | Prominent | Prominent | | **Dermal Invasion** | Early, dominant | Later | Later | Later | | **Location** | Any site | Trunk, extremities | Face, neck | Palms, soles, nails | | **Prognosis** | Worse (early VGP) | Intermediate | Better (early detection) | Worse (late diagnosis) | ### Clinical Pearl **High-Yield:** Nodular melanoma accounts for 15–30% of all melanomas but has the worst prognosis because it lacks a prolonged radial growth phase, allowing early vertical invasion before clinical detection. ### Prognostic Implications - Breslow thickness is typically >1 mm at presentation - Clark level IV–V involvement common - Higher mitotic rate and risk of metastasis - Rapid progression if not excised early **Mnemonic: NM = No Mess (no long RGP, goes straight down)** — contrasts with SSM which has a "messy" radial phase first. 
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