Dermoscopic Colours:

 

The most important pigment in the skin in dermoscopy is melanin. The colour of melanin in the skin provides important information about the anatomical location of the pigment. If melanin is located high up in the skin (i.e stratum corneum) then the melanin will appear black. If the pigment is lower down in the epidermis/ dermal-epidermal junction then it will appear brown. If the pigment is deeper in the dermis it will appear blue.

 

 

 

 

 

 

 

 

 

 

 

 

Pigment network:

 

A pigment network is formed by melanin in keratinocytes or melanocytes along the rete ridges of the epidermis. The melanin is more densely packed on the rete ridges and this forms the lines of the network. The holes represent the tips of the dermal papillae. A normal network is regular and tends to fade towards the periphery. Atypical networks are found in dysplastic naevi and melanomas.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dots and Globules:

 

Red dots represent small blood vessels whereas brown/grey/black dots represent melanin. The dots represent nests of melanocytes and can be produced after UV exposure. The difference between dots and globules is their size. Dots are less than 0.1mm whereas globules are larger. Globules are nests of benign or malignant melanocytes.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Blotches:

 

A blotch is a large homogenous area of pigment. Blotches are common in benign naevi but tend to be regular and central. When blotches are asymmetrical and off-centre melanoma needs to be excluded.

 

Streaks:

 

Streaks are linear projections at the edge of a lesion. They represent bridging of junctional nests of melanocytes. They are seen in spitz naevi as well as melanoma. In melanoma these represent the radial growth phase of the tumour and are usually found asymmetrically. In spitz naevi they tend to be symmetrically around the entire lesion as seen below.

 

 

 

 

 

 

 

 

 

 

 

 

 

Regression structures:

 

Regression represents an immune reaction with white scar-like areas and focal areas of fine granular pigmentation. Histologically the scar like areas represent fibrosis and the granular pigmentation represents melanin either free or in melanophages.