Structures used in pattern analysis

From dermoscopedia

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 Editor: Harald Kittler

 Author(s): Harald Kittler
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Description This chapter covers the structures and patterns used in pattern analysis
Author(s) Harald Kittler
Responsible author Harald Kittler→ send e-mail
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Status update December 5, 2019
Status by Ralph P. Braun


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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[edit]

Consists of lines of one or more of the five types defined below:

Reticular lines[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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[edit]

  • 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:
  1. One pattern at the center and the other at the periphery
  2. Vice versa
  3. 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