Dermoscopy
Dermoscopy significantly improves the sensitivity and specificity of diagnosing cutaneous melanoma and non-melanoma skin cancers compared to naked-eye examination.
The 2-Step Algorithm
The standard approach to evaluating any skin lesion with a dermatoscope involves two distinct steps to avoid diagnostic pitfalls.
Step 1: Is it Melanocytic?
Look for specific criteria that confirm the lesion is of melanocytic origin:
- Pigment network (typical or atypical)
- Aggregated globules
- Branched streaks
- Homogeneous blue pigmentation
- Parallel pattern (on acral skin)
If none are present, evaluate for non-melanocytic specific criteria (e.g., arborizing vessels for BCC, comedo-like openings for Seborrheic Keratosis).
Step 2: Is it Malignant?
If the lesion is melanocytic, apply a diagnostic algorithm to assess the risk of melanoma:
- Pattern Analysis: Asymmetry of color and structure.
- ABCD Rule: Asymmetry, Border, Color, Differential structures.
- 7-Point Checklist: Atypical network, blue-white veil, atypical vascular pattern, irregular dots/globules, irregular streaks, irregular blotches, regression structures.
Vascular Structures in Non-Pigmented Lesions
When pigment is absent, vascular morphology is the key to diagnosis.
| Vascular Pattern | Associated Diagnosis |
|---|---|
| Arborizing vessels (in focus, bright red, branching) | Basal Cell Carcinoma (BCC) |
| Crown vessels (surrounding a central white/yellow area) | Sebaceous Hyperplasia / Molluscum Contagiosum |
| Dotted vessels (regularly arranged) | Spitz Nevus / Clear Cell Acanthoma |
| Dotted / Glomerular vessels (clustered) | Bowen's Disease (SCC in situ) |
| Polymorphous (dots, linear irregular, corkscrew) | Amelanotic Melanoma |