Parallel ridge pattern

Dermoscopic Description
Pigment in the ridges of the dermatoglyphs (fingerprints) on the palms and soles

What the structures correspond to histologically
Melanin in the keratinocytes of the ridges, or haemoglobin in the subcorneal area of the ridges

Lesions in which the structures arise
Melanin in the ridges is strongly suggestive of melanoma. Subcorneal haemorrhage is the main differential diagnosis.