Symmetric blotch

Fig 1 Blotch

A blotch (fig 1)  is a dark-brown or black structure-less area where other dermoscopic features cannot be seen. Symmetric blotches are in favour of benign lesions. Assymetrically distributed blotches are in favour of melanomas.

In our case, the blotch was symmetrically disposed and a peripheral reticular network was visible. This kind of blotch is also called black lamella.

This lesion was corresponding to a benign melanocytic nevus.

It has to be distinguished from the blue structure-less pattern or blue homogeneous pattern of a blue nevus (fig 2).

Fig 2 Blue homogeneous pattern

Blotch

Blotch (or black lamella) is a black or dark brown pigmentation.
Blotch is formed by a large quantity of melanin pigment in the epidermis and / or dermis.
Here is a case of melanocytic junctional nevus where a blotch is covering its largest area.
In malanomas, blotches are often irregular.