Like every basic element pigmented by melanin (i.e., dots, clods, lines, pseudopods, and circles) each type of vessel may form a pattern. A pattern is defined as a collection of multiple vessels covering a significant part of the lesion. If one type of vessel is dominating by far, the vascular pattern is termed monomorphic. If more than one type of vessel is present, the pattern is termed polymorphic.

As a rule, a pattern is formed by multiple vessels that appear to be distributed in a random fashion and are not arranged in a specific way. However, it is important to note that there are some exceptions (Fig. 2). If vessels that appear as dots or coiled vessels are not evenly distributed but concentrated in certain areas we call this pattern clustered. If vessels that appear as dots or coiled vessels are arranged in a linear, arciform pattern, we call that specific arrangement serpiginous. Linear vessels (of the type straight, curved, or looped) at the periphery that are orientated towards the center of the lesion but are not crossing it are termed radial. Linear straight vessels may cross each other and may be arranged in a way similar to pigmented lines reticular. We therefore call this vascular pattern reticular. Finally, multiple serpentine vessels may divide from a main stem (usually a thick serpentine vessel), a pattern which is termed branched.