Structures used in pattern analysis
From dermoscopedia
Basic elements
Lines: structures with parallel edges, with their length much greater than their breadth
Dots: circumscribed, small, round, indivisible pigmented structures with no length or breadth
Clods: solid, circumscribed, diversely formed pigmented or unpigmented structures larger than dots, with length and breadth
Circles: lines or collection of pigmented dots arranged sensibly equidistant from a common focal point that constitutes the center
Pseudopods: short pigmented lines with a bulbous end
Basic patterns
Every basic element may be part of a pattern. Multiple repetitions of the same single basic element are required to constitute a pattern. This collection of basic elements should comprise a significant portion of the pigmented lesion (~ 25%).
Lines
Consists of lines of one or more of the five types defined below:
Reticular lines
- Straight and arranged in such a manner that they intersect each other nearly at right angles in regular intervals to form a net-like structure.
- They may be thin or thick.
Branched lines
- Straight and arranged such that they intersect each other, but not at regular intervals and not at right angles.
- May be thin and thick lines simultaneously.
- They can also intersect each other, but not always at right angles.
- Typically one finds several thin lines originating from a thick one (right figure, white rectangle).
Parallel lines
- They are straight and arranged in parallel fashion, i.e. they do not intersect.
- Mainly found on acral skin, but also on the nails.
- May be thick or thin.
- On acral skin, they may be arranged on ridges, in furrows, or crossing the ridges and furrows.
Radial lines
- They converge at a single dot or clod, or at a common point if extended.
- At a lesion’s periphery, they may occupy the entire circumference, or be confined to one segment.
- This pattern is always found in combination with another pattern.
Curved lines
- They are not straight but curved, have few intersections, and may be parallel or distributed randomly.
- Usually occur in pairs.
- May be short or long, and thin or thick.
Dots
- Dots are small and indivisible, always of the same shape, and nearly the same size.
- They have neither length nor breadth.
- Arranged in a pattern may be densely arranged or sparse.
Pattern of clods
- A pattern of clods is a collection of clods, that may have different sizes and different shapes.
- The individual clods in a pattern of clods may be densely arranged or sparse.
Pattern of circles
- A collection of circles is termed a pattern of circles.
- They may be found anywhere, however they mostly occur in pigmented lesions on the face.
- Circles may be densely arranged or sparse.
- Due to the large number of follicular openings and the absence of rete ridges, they are very often seen on the face.
- Pigmented circles may occur at any site of the body.
Pattern of pseudopods
- Consists of a collection of pseudopods at the periphery of the lesion or at the periphery of a well-defined structure within a lesion.
- Pseudopods may involve the entire periphery, or few segments.
- Always occurs in combination with another pattern.
Structureless pattern
- Absence of a dominant basic element. It should be a coherent area.
- Needs not be homogeneous or even completely structureless; one usually finds a certain degree of ”noise”. However, there are too few of any basic element present to form a pattern.
Combinations of patterns
- A pigmented lesion may be composed of one or more patterns.
- The combination of patterns may be symmetrical or asymmetrical; Symmetry exists when the lesion’s pattern can be mirrored in any conceivable axis.
- When a lesion consists of two patterns there may be three types of symmetrical combinations:
- One pattern at the center and the other at the periphery
- Vice versa
- Elements of one pattern (usually dots or clods) regularly distributed within the other pattern
- When a pigmented lesion consists of three patterns, symmetry in all axes is ensured only when these are arranged concentrically (like a target).
- The more numerous the patterns, the greater is the likelihood of their being asymmetrical
