Normal acral anatomy:

 

In order to understand the dermoscopic features of pigmented lesions on acral skin it is essential to appreciate the unique anatomy of the skin in those areas. The undulating surface gives rise to fingerprints (dermatoglyphs) with the alternating ridges and furrows.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In benign naevi, melanocytes tend to transfer melanin to the keratinocytes associated with the crista limitans associated with the furrows (giving the classical benign parallel furrow pattern). In melanoma, however, the malignant melanocytes tend to cluster around the crista intermedia giving the parallel ridge pattern.

 

 

Benign acral dermoscopic patterns:

 

The main benign acral patterns are:

1) Parallel furrow pattern

2) Lattice pattern

3) Fibrillar pattern

 

 

Malignant acral dermoscopic patterns:

 

The main malignant acral pattern is the parallel ridge pattern. Other patterns include the multi-component pattern. The parallel ridge pattern is commonly seen in in-situ ALMs.