Pattern analysis

From dermoscopedia

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Introduction

  • “Simplified” algorithms such as the ABCD rule, the 7-pointThis glossary term has not yet been described. checklistThis glossary term has not yet been described., the CASH algorithmIn mathematics and computer science, an algorithm (Listeni/ˈælɡərɪðəm/ AL-gə-ri-dhəm) is a self-contained sequence of actions to be performed. Algorithms can perform calculation, data processing and automated reasoning tasks., or Menzies' method were developed as uncomplicated and easily assimilated guidelines for daily use. These algorithms are easy to learn but, with the exception of Menzies' method, not easy to apply.
  • Menzies' method is the only scoring system that follows an initial screening based on an overall assessment of pattern and colorColor (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. to determine whether a detailed investigation is worthwhile.
  • The sequence of assessment, first pattern, then color, and finally cluesThis glossary term has not yet been described., concurs exactly with the approach of pattern analysis. Menzies' method is a highly simplified version of the algorithms of pattern analysis, but limited to melanocyticThis glossary term has not yet been described. lesions.
  • Simple and easily learned rules of thumb based on pattern analysis can be formulated, that fulfill the demand for a rapid and uncomplicated algorithm, but without this restriction to melanocytic lesions (chaos and cluesThis an algorithm used in dermoscopy [[Chaos and Clues]])
  • The basics of pattern analysis are easy to learn, but its application is sometimes complex and needs experience.

Structure

Basic elements

Linesstreaks: structures with parallel edges, with their length much greater than their breadth

DotsThis glossary term has not yet been described.: circumscribed, small, round, indivisible pigmented structures with no length or breadth

Clods: solid, circumscribed, diversely formed pigmented or unpigmented structures larger than dotsThis glossary term has not yet been described., with length and breadth

Circles: lines or collection of pigmented dots arranged sensibly equidistant from a common focal point that constitutes the center

PseudopodsBulbous and often kinked projections seen at the lesion edge, either directly associated with a network or solid tumor border.: 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%).

Pattern of linesstreaks

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

Reticular linespigment network melanocytic lesions dermatofibroma solar lentigo

  • 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 acralAcral melanoma is a type of skin cancer that occurs on fingers, palms, soles, and nail beds. skinThis glossary term has not yet been described., 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 dotSee [[Glossary:Dots|Dots]] 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.


Pattern of 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 faceThis glossary term has not yet been described..
  • 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 pseudopodsBulbous and often kinked projections seen at the lesion edge, either directly associated with a network or solid tumor border.

  • 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:
  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


ColorColor (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue.

Melanin

  • Depending on the layer of skin in which melanin is located, it may appear:
  1. Black: when located in the stratum corneum
  2. Brown: when located in the basal layers of the epidermis
  3. Gray: when located in the papillary dermis
  4. Blue: when located in the reticular dermis
  • The observed color depends on the density of melanin and the thickness of the epidermis:
  1. Dark-brown or nearly black: dense accumulation in the basal layer of the epidermis
  2. Light-brown: less dense accumulation
  3. Blue: the epidermis is thickened due to acanthosis (e.g. some seborrheic keratosesThis glossary term has not yet been described.)

Other pigments

Hemoglobin

Pigment ranges from bright red to blue, depending on the level of oxygen saturation in vesselsThis glossary term has not yet been described.

  • Dark red: coagulated blue, due to massive extravasation of red blood cells (i.e. hemorrhage)
  • Black: blood in the stratum corneum (corneal bleeding)
  • Red to blue: fresh blood in the dermis.
  • Green to brown: due to degradation of hemoglobin
  • Orange: in cases of eroded lesions, that serum flows out of the surface, dries, and forms a crust.
  • Orange to yellow: mixture of the white or yellow of keratin with the brown of melanin (e.g. pigmented seborrheic keratoses)
  • White: fibrosis or sclerosis of the dermis


Chaos and cluesThis an algorithm used in dermoscopy [[Chaos and Clues]]

  • It is designed to be applied to any pigmented skin lesion to rapidly detect any type of malignancy, or to guide the clinician in the decision whether a lesion should be excised or biopsied rather than to make a specific diagnosisThis glossary term has not yet been described..
  • The clinical and dermatoscopical examination for chaos is being defined as asymmetry of structure or color.
  • When chaos is discovered, the lesion is being searched for one of eight clues to malignancy.
  • If there are both chaos and at least one clue to malignancy then biopsy is indicated.

Chaos

  • Definition: asymmetry produced by the pattern of structures or colors within a lesion.
  • Any color other than skin color at the edge of a lesion (such as white) should be regarded as part of the lesion.
  • A lesion with one pattern and one color, regardless of its shape, is symmetrical and therefore does not exhibit chaos. If any line drawn through the center of a lesion has different colors or structures on opposite sides it is asymmetrical and exhibits chaos.
  • Lesions without chaos are not analyzed any further.
  • It is very rare to find perfect symmetry in nature. If a decision cannot be made the lesion should be assessed as exhibiting chaos.


CluesThis glossary term has not yet been described. to Malignancy

  • Definition: a feature which indicates that a lesion requires a biopsy to exclude malignancy. One clue is sufficient.
  • There are eight clues to pigmented malignancy (melanomaThis glossary term has not yet been described., pigmented basal cell carcinomaThis glossary term has not yet been described. (pBCC), and pigmented BowenThis glossary term has not yet been described.’s disease (pBD).
  1. Eccentric structureless areahomogenous pattern various diagnoses: any color except skin color.
  2. Gray or blue structures: Gray dots may be seen in pBCC and pBD as well as melanoma. Gray circles occur in noninvasive facial melanomas.
  3. Black dots or clods, peripheral: They are generally produced by melanoma cells or nests, respectively.
  4. Lines radial or pseudopods, segmental: Lines radial may be seen at any location in BCC. Pseudopods or lines radial when circumferential area feature of Reed nevusThis glossary term has not yet been described., but if segmental they are highly specific for melanoma.
  5. Polymorphous vesselsmultiple types of vessels are present may indicate malignancy in appropriate context for example in flat melanocytic lesions: VesselsThis glossary term has not yet been described. are called polymorphous when more than one pattern of vessel is seen. They reflect disordered malignantThis glossary term has not yet been described. growth pattern and possibly increased metabolic demand of actively growing tumor tissue.
  6. White lines: To qualify as a clue, they must be clearly lighter than perilesional skin.
  7. Lines reticular or branched, thick: To be called thick, the lines must be thicker than the spaces they surround. They are produced by melanoma cells.
  8. Lines parallel, ridges (acral skin): Clue to malignancy even in the absence of chaos. Subcorneal hemorrhage also produces this pattern.

Full pattern analysis

  • Pigmented skin lesions can be described very clearly and reliably with the aid of the patterns, colors and clues.
  • Pattern analysis is a structured description in the form of an algorithm with fixed and reproducible rules.

The algorithm always follows this formula:

Pattern + Color + Clues = DiagnosisThis glossary term has not yet been described.

  • Based on patterns, colors and clues, the number of potential diagnoses is minimized.
  • In cases in which it is not possible to dispel all doubts in respect of the diagnosis, the degree of doubt and the type of possible diagnoses will be decisive factors to determine whether a histopathological investigation should be performed.




References

  1. An Atlas of DermoscopyDermoscopy is a non invasive diagnostic method., Second Edition. Marghoob A. et al. CRC Press; 2012.
  2. Altamura, D., Menzies, S.W., Argenziano, G., et al., 2010, DermatoscopyThis glossary term has not yet been described. of basal cell carcinomais the most common skin cancer, and one of the most common cancers in the United States.[1] While BCC has a very low metastatic risk, this tumor can cause significant disfigurement by invading surrounding tissues: morphologic variability of global and local features and accuracy of diagnosis. J Am Acad Dermatol, 62, 67–75.
  3. Argenziano, G., Soyer, H., Chimenti, S., et al., 2003, Dermoscopy of pigmented skin lesions: results of a consensus meeting via the Internet. J Am Acad Dermatol, 48, 679–93.
  4. Binder, M., Kittler, H., Steiner, A., et al., 1999, Reevaluation of the ABCD rule for epiluminescence microscopy. J Am Acad Dermatol, 40(2 Pt 1), 171–6.
  5. Binder, M., Schwarz, M., Winkler, A., et al., 1995, Epiluminescence microscopy. A useful tool for the diagnosis of pigmented skin lesions for formally trained dermatologists. Arch Dermatol, 131, 286–91.
  6. Braun, R.P., Gaide, O., Oliviero, M., et al., 2007, The significance of multiple blue-grey dots (granularityThis glossary term has not yet been described.) for the dermoscopic diagnosis of melanoma. Br J Dermatol, 157, 907–13.
  7. Cameron, A., Rosendahl, C., Tschandl, P., Riedl, E. & Kittler, H., 2010, Dermatos- copy of pigmented Bowen’s disease. J Am Acad Dermatol, 62, 597–604.
  8. Chamberlain, A.J., Fritschi, L. & Kelly, J.W., 2003, Nodular melanomaThis glossary term has not yet been described.: patients’ per- ceptions of presenting features and implications for earlier detection. J Am Acad Dermatol, 48, 694–701.
  9. Kittler, H., 2007, Dermatoscopy: introduction of a new algorithmic method based on pattern analysis for diagnosis of pigmented skin lesions. Dermatopathol Pract Conc, 13, 1.
  10. Kittler, H., Riedl, E., Rosendahl, C. & Cameron, A., 2010, Dermatoscopy of unpig- mented lesions of the skin: a new classificationThis glossary term has not yet been described. of vessel morphologyThis glossary term has not yet been described. based on pattern analysis. Dermatopathol Pract Conc, 14, 3.
  11. Menzies, S.W., Crotty, K.A. & McCarthy, W.H., 1995, The morphologic criteriaThis glossary term has not yet been described. of the pseudopod in surface microscopy. Arch Dermatol, 131, 436–40.
  12. Pehamberger, H., Steiner, A. & Wolff, K., 1987, In vivo epiluminescence microscopy of pigmented skin lesions. I. Pattern analysis of pigmented skin lesions. J Am Acad Dermatol, 17, 571–83.