The first step algorithm for dermoscopy distinguishes melanocytic lesions from non-melanocytic lesions. It is used to evaluate pigmented lesions.
Look for specific features of a melanocytic lesion. If these are absent, look for specific features to diagnose pigmented basal cell carcinoma, seborrhoeic keratosis or haemangioma. Also consider whether the lesion could be a viral wart or dermatofibroma (look for the central white patch). If none of these lesions can be diagnosed, treat the lesion as melanocytic (see above).
Benign and malignant melanocytic lesions have one or more of the following characteristics:
Seborrhoeic keratoses have the following characteristics:
Pigmented basal cell carcinomas have the following characteristics:
Haemangiomas have the following characteristics:
The second step is to distinguish benign melanocytic lesions from malignant melanoma using one of the following methods.
If these algorithms appear too complicated, use the 3-point checklist, which is a safe way to identify malignant pigmented lesions.
Practice identifying melanocytic and non-melanocytic pigmented lesions by dermoscopy.
See the DermNet NZ bookstore.
© 2019 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.