Malignant Melanoma
A malignant tumor arising from melanocytes, primarily in the skin. It is the most deadly form of skin cancer, characterized by rapid metastasis if not treated in the early stages.
The ABCDE Criteria
- A – Asymmetry: One half of the lesion does not match the other.
- B – Border: Irregular, scalloped, or poorly defined edges.
- C – Color: Variability in color (shades of brown, black, blue, red, or white).
- D – Diameter: Typically >6 mm (though smaller lesions can be melanomas).
- E – Evolving: The lesion is changing in size, shape, color, or symptoms (e.g., itching, bleeding).
Prognostic Factors & Management
| Factor | Significance |
|---|---|
| Breslow Depth | The most important prognostic factor measures the depth of tumor invasion in millimeters. |
| Treatment | Wide surgical excision; sentinel lymph node biopsy for staging; immunotherapy/targeted therapy for advanced disease. |
High-Yield Exam Pearl:
- Subtypes: Superficial spreading is the most common. Nodular has the worst prognosis due to its rapid vertical growth phase. Acral lentiginous is the most common form in patients with darker skin types and is not necessarily sun-related.
- Radial vs. Vertical Growth: Melanoma starts with a radial growth phase (horizontal spread) before transitioning to a vertical growth phase (invasion into the dermis), which significantly increases the risk of metastasis.