Dermoscopic rainbow pattern: A strong clue to malignancy or just a light show?

Area of Science:

• Dermatology
• Dermoscopy
• Oncology

Background:

• The rainbow pattern is a dermoscopic finding characterized by multiple colors.
• It is traditionally associated with Kaposi sarcoma.
• However, its presence in other conditions warrants investigation.

Purpose of the Study:

• To report non-Kaposi sarcoma conditions exhibiting a dermoscopic rainbow pattern.
• To discuss the diagnostic significance of this finding in a broader context.

Main Methods:

• A multicenter review of dermoscopic images from histopathologically diagnosed lesions.
• Inclusion criteria: presence of a dermoscopic rainbow pattern in non-Kaposi sarcoma lesions.
• Standardized dermoscopic examination using a polarized handheld dermoscope (x10 magnification).

Main Results:

• Twenty-one (2%) of 840 reviewed lesions showed a dermoscopic rainbow pattern.
• Commonly affected lesions included pyogenic granuloma and hypertrophic scar (19% each).
• Other reported lesions: basal cell carcinoma, dermatofibroma, angiokeratoma, blue nevus, granuloma annulare, strawberry angioma, epidermal cyst, malignant melanoma, dissecting cellulitis, and subungual hematoma.

Conclusions:

• The rainbow pattern is a non-specific optical phenomenon observed in both vascular and non-vascular lesions.
• Its diagnostic value depends on other accompanying dermoscopic features.
• This study is the most comprehensive on rainbow patterns in non-Kaposi lesions, reporting it in dissecting cellulitis, granuloma annulare, and subungual hematoma for the first time.