Analytic approach

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The analytic approach

Definition: An algorithmic method for the diagnosisThis glossary term has not yet been described. of pigmented lesions

The essence of pattern analysis is a structured description formulated using a clearly defined algorithmic method. The diagnostic method is structured in such a way that one starts by describing the most general of features, then proceeds progressively to finish with the most specific features.

The 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. always takes the general form:

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

Using patterns, colors and cluesThis glossary term has not yet been described., the number of potential diagnoses is progressively minimized. Pattern is a method by which algorithms are constructed.

One pattern

A pattern is formed by an aggregation of one of the five basic elements: linesstreaks, pseudopodsBulbous and often kinked projections seen at the lesion edge, either directly associated with a network or solid tumor border., circles, clods and dotsThis glossary term has not yet been described..

When basic elements are not seen or there are too few basic elements to constitute a pattern, the "pattern" is termed structureless.

Linesstreaks

Lines may form six different patterns, depending on their shape and arrangementThis glossary term has not yet been described.: reticular, branched, angulated, parallel, radial, and curved.

Reticular linespigment network melanocytic lesions dermatofibroma solar lentigo

Lesions with reticular linespigment network melanocytic lesions dermatofibroma solar lentigo are not always melanocyticThis glossary term has not yet been described.. In most cases the histological correlate of reticular lines is hyperpigmentation of basal keratinocytes, which may or may not be created by an increase in the numbers of melanocytes.

Color

  • Usually light-brown or dark-brown, due to melanin in the epidermis.
  • If the pigment is very dense, the lines are black.
  • Rarely, they can appear gray.

Not every shade of brown is to be interpreted as a separate 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.. One or two black lines do not render the lesion multicolored. The normal hypopigmentation around follicular openings does not create an extra color. Nearly all pigmented lesions are somewhat lighter at the periphery than in the center.

Light-brown + thin reticular lines: junctional Clark nevus or solar lentigoThis glossary term has not yet been described..

  • A Clark nevus is round or oval and the pigmentation does not end abruptly at the periphery.
  • The border of a solar lentigo is usually sharply demarcated and scalloped.
  • Differential diagnoses: a variant of dermatofibromaThis glossary term has not yet been described. with reticular lines only and urticaria pigmentosa, a type of mastocytosisThis glossary term has not yet been described..

Brown reticular lines + thick: Clark nevus or superficialThis glossary term has not yet been described. congenital nevusThis glossary term has not yet been described..

  • Differential Diagnoses: Solar lentigoThis glossary term has not yet been described., seborrheic keratosisThis glossary term has not yet been described..

Black (very dark-brown) reticular lines: ink-spot lentigo.

  • No differential diagnosis needs to be considered. Very rarely a Reed nevusThis glossary term has not yet been described. may demonstrate this pattern and color combination, but without the additional clues to "ink-spot lentigo".

More than one color + reticular lines: solar lentigo or seborrheic keratosis.

  • Clues to solar lentigo: well-demarcated, scalloped border.
  • Clues to seborrheic keratosis: white dots or clods, orange or yellow clods, well-demarcated border, circles, thick curved lines, vesselsThis glossary term has not yet been described. as loops or coils.
  • Differential diagnoses: Clark nevus, "superficial" or "superficial and deep" congenital nevus, and in situThis glossary term has not yet been described. melanomaThis glossary term has not yet been described.

Dark-brown or black and light-brown areas: variegate color distribution.

  • Differential diagnosis: Clark nevus, "superficial" or "superficial and deep" congenital nevus, or in situ melanoma
  • Only 5 of the 8 clues to melanoma are seen in reticular patternA lesion with a reticular pattern has typical pigment network throughout the entire lesion. lesions: a) gray dots, clods, circles or lines; b) radial lines or pseudopods seen only in some segments of the periphery; c) black dots or clods at the periphery d) thick reticular lines and e) angulated lines (polygonsThis glossary term has not yet been described.). When one of these clues is present, the diagnosis of melanoma should be seriously considered.

Eccentric hyperpigmentation, i.e. the more heavily pigmented area is not in the center but the periphery: Clark neviThis glossary term has not yet been described. and in situ melanomas, rarely in congenital neviThis glossary term has not yet been described..

  • Differential diagnosis: MelanomaThis glossary term has not yet been described.. When no clue to melanoma is present, a Clark nevus is the most likely diagnosis.
Branched lines

Branched lines and reticular lines are closely related and often occur together. Lesions that are exclusively composed of branched lines are either black or brown, and they are all benignThis glossary term has not yet been described..

  • Brown branched lines: Clark nevus or "superficial" or "superficial and deep" congenital nevus.
  • Black (or very dark-brown) branched lines: "ink-spot" lentigo.
Angulated lines
  • May appear on facial skin and on non-facial skinThis glossary term has not yet been described..
  • They are the hallmark of flat melanomas on chronic sun-damaged skin.
  • Most melanomas with angulated lines are not invasive (in situ).
  • They are usually brown or grey.
Parallel lines
  • Typical pigment pattern of acralAcral melanoma is a type of skin cancer that occurs on fingers, palms, soles, and nail beds. skin.
  • They may be arranged in one of three ways; on the ridges (ridgeThis glossary term has not yet been described. pattern), in the furrows (furrow pattern), or crossing ridges (crossing pattern).
  • AcralAcral melanoma is a type of skin cancer that occurs on fingers, palms, soles, and nail beds. lesions that only show a pattern of furrows or a crossing pattern may be safely considered to be benign.
  • Assessment of a lesion showing the ridge pattern proceeds by evaluating color.
  • If it is brown, in situ melanoma must be considered. Black, red or purple parallel lines on the ridges indicate either hemorrhage or exogenous pigmentation. Satellite clods are a strong clue to the diagnosis of hemorrhage.
Radial lines
  • They always occur in combination with another pattern.
Curved lines
  • They usually occur in combination with other patterns.

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

  • They occur only in combination with other patterns.

Circles

  • It is the pattern of facial skin, but also not unusual at other locations on the body.

On the faceThis glossary term has not yet been described., they are formed by melanin pigment arranged either around the openings of the crater-like infundibula or in infundibular epithelium. The center of the infundibulum appears hypopigmented. If infundibula contain keratinized material the hypopigmented center is seen as a yellow or orange clod.

They may be brown, gray or black.

  • Brown circles: solar lentigo or flat seborrheic keratosis.
  • Gray circles on facial lesions: melanoma in situ.
  • Differential diagnoses: lichen planusThis glossary term has not yet been described.-like keratosis, pigmented actinic keratosisActinic keratosis (also called solar keratosis and senile keratosis; abbreviated as AK) is a pre-cancerous patch of thick, scaly, or crusty skin. These growths are more common in fair-skinned people and those who are frequently in the sun. They usually form when skin gets damaged by ultraviolet (UV) radiation from the sun or indoor tanning beds. AKs are considered potentially pre-cancerous; left untreated, they may turn into a type of cancer called squamous cell carcinoma. Untreated lesions have up to a 20% risk of progression to squamous cell carcinoma, so treatment by a dermatologist is recommended., in situ melanoma.
  • On the trunk or the extremities the pattern of circles may be a variant of the reticular pattern.
  • Differential diagnoses: junctional Clark nevus, solar lentigo, dermatofibroma

Clods

After reticular lines, the pattern of clods is the second most common.

One color predominates
  • White and/or yellow clods: Seborrheic keratosisThis glossary term has not yet been described., dilated infundibula and inclusion cysts ("milia") filled with keratin, sebaceous gland hyperplasia.
  • Radial vesselscrown vessels Radial serpentine or arborizing vessels at the periphery of the lesion that radiate towards the center but do not cross the midline od the lesion. sebaceous hyperplasia which do not cross the center of the lesion are a strong clue to sebaceous gland hyperplasia.
  • Orange clods: Seborrheic keratosis, or 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 (orange clods due to ulceration (serum crust)).
  • Whereas multiple orange clods are seen in seborrheic keratosis, in basal cell carcinoma one usually finds one or two orange clods with traces of red due to red blood cells in the serum crust. A further clue is the pattern of vessels: in basal cell carcinoma serpentine vesselslinear irregular linear vessels with multiple bends flat BCC melanoma, often branched; in seborrheic keratosis, looped or coiled vesselsglomerular vessels tightly coiled vessels resembling the glomerular apparatus of the kidney Bowen disease (or rarely serpentine).
  • Red or purple clods: hemangioma or vascular malformations.
  • Thrombosed vessels are seen as black clods. Hemorrhage may be seen as red clods.
  • Large, polygonal skin-colored clods: exophytic congenital nevi with papillomatous surface (Unna nevus or Miescher nevus), or verrucous seborrheic keratosis.
  • Brown clods: various types of melanocytic nevi.
  • Large, polygonal light-brown clods: Unna nevus or Miescher nevus
  • Small to medium-sized, round and oval brown clods: small congenital nevi, of "superficial" and "superficial and deep" types.
  • Central hyperpigmentation is common in pigmented Spitz neviThis glossary term has not yet been described., and peripheral clods are usually smaller than those in the center.
  • Blue clods: pigmented basal cell carcinomaThis glossary term has not yet been described..
  • Differential diagnoses: While melanoma and combined congenital nevus.
More than one color

Necessary to distinguish between the colors of melanin and the colors of other pigments Clods whose pigmentation is due to melanin are brown, blue or gray.

  • Black clods: blood pigment hemoglobin.
  • White, yellow or orange clods: keratin with (orange) or without (white or yellow) inclusions of melanin. Orange clods may also result from ulceration (serum crust).
  • White or yellow clods are mainly found in seborrheic keratosesThis glossary term has not yet been described. and less often in Unna nevi. Orange clods also indicate a seborrheic keratosis or less often an Unna nevus.
  • Combination of red, purple or black clods: hemangioma, vascular malformation or hemorrhage.
  • Clods + colors of melanin (brown, blue or gray): symmetry of color distribution is assessed next.
  • Symmetrical color distribution: melanocytic nevi, i.e. superficial and deep congenital nevi, combined congenital nevi, Unna nevi and pigmented Spitz nevi
  • Asymmetrical color distribution: pigmented basal cell carcinoma and melanoma.

DotsThis glossary term has not yet been described.

It occurs in combination with other patterns. The diagnosis proceeds by assessing color:

  • Only gray or brown dots are found in lesions without another pattern.
  • Only red dots: non-pigmentedThis glossary term has not yet been described. lesion, i.e. vessels as dots.
  • Gray dots: lichen planus-like keratosis (solar lentigo in regressionThis glossary term has not yet been described.), pigmented actinic keratosis, pigmented BowenThis glossary term has not yet been described.’s disease, melanoma.


Differential diagnoses:

  • Lichen planusThis glossary term has not yet been described.-like keratosis: curved lines or typical sharply defined and scalloped border. On chronic UV-exposed sites (face or the dorsum of the hand).
  • Pigmented actinic keratoses: on the face. Usually seen as gray circles
  • Pigmented Bowen’s disease: on the trunk and extremities. It may mimic other lesions, but the clues of coiled vessels and dots arranged as lines lead to the correct diagnosis.
  • In situThis glossary term has not yet been described. melanomas: gray dots mixed with brown dots. Random distribution, arranged as circles around the openings of the infundibula (face), or lines arranged as polygons (trunk or extremities)


  • Brown and small gray dots: Clark nevus, or rarely solar lentigo and pigmented Bowen’s disease.
  • Brown and red dots: inflammatory skin diseases with extravasation of red blood cells, e.g. pigmented purpuric dermatosis.

Structureless

Definition: no basic elements, too few to constitute a pattern, or the visible structures cannot be assigned to one of the five basic elements.

Lesions that only have a structureless pattern are difficultThis glossary term has not yet been described. to diagnose using dermatoscopyThis glossary term has not yet been described. and often require histopathologyThis glossary term has not yet been described..

One color predominates over all others
  • Black + structureless: presence of hemoglobin (not melanin) and its degradation products, e.g. hemorrhagic crusts, hemorrhages in the epidermis and thrombosed vessels.
  • Differential diagnoses: heavily pigmented melanocytic lesions, e.g. Reed nevus, Clark nevus or melanoma.
  • Blue + structureless: "blue nevi" of all types.
  • Differential diagnoses: melanomas melanoma metastases, structureless blue pigmented basal cell carcinomas.
  • Brown + structureless: solar lentigo, flat seborrheic keratosis, pigmented Bowen’s disease, melanocytic nevus of "superficial" or "superficial and deep" congenital type.
  • Red + structureless: recent hemorrhage in the stratum corneum. This will become a black structureless lesion as the hemoglobin degrades, before it entirely disappears due to transepidermal elimination.


More than one color

DifficultThis glossary term has not yet been described. to decide whether clods or structureless. Clods: well circumscribed and always occur in numbers. Structureless: one large contiguous area.

  • Colors of keratin (yellow and orange): keratinizing lesions such as seborrheic keratosis.
  • Differential diagnoses: basal cell carcinoma
  • Colors of hemoglobin (red and purple): hemorrhage, or hemorrhage in a pre-existing lesion such as a nevus.
  • Black zones in structureless lesion: thrombosis.
  • Differential diagnoses: black should be attributed to blood when it appears together with red or purple and attributed to melanin when it appears together with brown, blue or gray.
  • Symmetrical distribution of melanin: nevus.
  • Asymmetrical distribution of melanin: melanoma, melanoma metastasis, seborrheic keratosis.
  • Differential diagnosis: pigmented basal cell carcinoma or a dermatofibroma.

More than one pattern

  • The majority of pigmented lesions have more than one pattern.
  • To constitute a pattern, multiple repetitions of a given basic element must be found, in an area occupying a significant part of a lesion.
  • The algorithm for pigmented lesions with more than one pattern is constructed in a hierarchical manner. The sequence starts with the pattern of lines and ends with the pattern of dots. When a pattern of lines is present, the algorithm for patterns of lines is followed. When no pattern of lines is present, the investigator looks next for pseudopods, then for circles, then clods, and finally for dots.
  • Presence or absence of structural symmetry: Symmetry is judged on the distribution of colors within the lesion. The more patterns, the less symmetry.
  • Two patterns combine symmetrically in three ways:

a) one pattern is in the center and the other at the periphery b) the opposite is the case c) the basic elements of one pattern (e.g. dots) are regularly spread over a second pattern (e.g. reticular lines).

  • All other combinations of two patterns are, by definition, asymmetrical.


Lines

Reticular and/or branched lines
  • Reticular lines are much more common than branched lines.


Sharply demarcated pattern

  • Sharply demarcated scalloped bordermoth eaten border solar lentigo + curved lines: solar lentigo or lichen planus-like keratosis.
  • Sharply demarcated borderThis glossary term has not yet been described., white dots or clods, yellow or orange clods + thick curved lines: seborrheic keratosis.


Symmetrical pattern

  • Clods in the center + reticular lines at the periphery: "superficial" or "superficial and deep" congenital nevus, Clark nevi.
  • Reticular lines in the center + clods (or dots) peripherally: Clark nevus in phase of growth, or growing superficial or superficial and deep congenital nevus.
  • Reticular lines + uniformly distributed clods (or dots): Clark nevi or "superficial" or "superficial and deep" congenital nevi.


Symmetrical color

  • SkinThis glossary term has not yet been described.-colored: raised and papillomatous. Most commonly in "superficial and deep" congenital nevus, less frequently in Clark nevus.
  • Dark-brown or black: Clark nevus, or rarely Reed nevus.
  • Blue: combined congenital nevus, or less often Reed nevus.
  • White: dermatofibroma.


  • Symmetrical combination of pseudopods (i.e. the pseudopods are seen occupying the entire circumference): Reed nevus.
  • Symmetrical combination of peripheral radial lines: Reed nevus, or Clark nevus.
  • Symmetrical combinations of three patterns, e.g. structureless in the center and reticular lines and dots or clods at the periphery: "superficial" and "superficial and deep" congenital nevi
  • Asymmetrical combination of patterns: usually exclusively brown and likely to be a nevus (Clark nevus or "superficial" or "superficial and deep" congenital nevus).
  • Asymmetrical lesions with more than one pattern (most lesions) should be assessed for clues to melanoma.
Parallel lines
  • Commonly seen in acral pigmented lesions.

They may appear on the ridges, in the furrows, or crossing ridges and furrows.


RidgeThis glossary term has not yet been described. pattern

  • It takes precedence if more than one parallel line pattern is seen.
  • Symmetry of pattern combination is secondary to the color of the ridge pigmentation.
  • If pigmentation on the ridges is in the colors of melanin, the diagnosis of melanoma must be considered. Hemorrhage or exogenous pigmentation are the likely diagnoses when colors other than those of melanin are seen.


Pattern of furrows or crossing pattern

  • Distinction between symmetrical and asymmetrical is necessary.
  • Symmetrical combinations: classical acral nevi and other nevi, e.g. Reed nevi or "superficial" and "superficial and deep" congenital nevi.
  • Asymmetrical combinations: clues to melanoma.
Radial lines
  • Always occur in combination with other patterns.


Symmetrical pattern

  • Radial lines occupy the entire circumference of the lesion.
  • Structureless center + white: dermatofibroma.
  • Structureless center + brown, black or gray: Reed nevus.


Asymmetrical pattern

  • Peripheral radial lines do not occupy the entire circumference of the lesion but are present only in some segments.
  • Primary differential diagnosis: melanoma versus basal cell carcinoma.
  • Two arrangements of radial lines, which usually have a common base. The radial lines are not only seen at the periphery but also within the lesion.


Curved lines
  • The least specific pattern. Lesions almost always asymmetrical.
  • Brown color: solar lentigo, seborrheic keratosis.
  • Colors of melanin (gray, blue or black): melanoma, seborrheic keratosis, lichen planus-like keratosis.

Pseudopods

They are only seen in combination with another pattern.

Usually at the periphery with other pattern in the center of the lesion: structureless, clods, or reticular lines.

Symmetrical pattern: regularly distributed pseudopods in the periphery, e.g. Reed nevus.

Asymmetrical pattern: melanoma must be considered.

Patient’s ageprocess of becoming older, skin typeThis glossary term has not yet been described., number of nevi, distribution of pseudopods, clinical appearance and history of change are relevant to the diagnosis.


Circles

Typical pattern of facial skin.

Symmetrical pattern: peripheral brown circles combined with a structureless zone (or less often white lines) centrally, e.g. dermatofibroma.

Asymmetrical pattern: pattern of circles with no lines. The color of the circles becomes more important than assessment of symmetry: Brown: solar lentigo, seborrheic keratosis, "superficial" or "superficial and deep" congenital nevus, Clark nevus, Miescher nevus. Gray or black: melanoma, lichen planus-like keratosis and pigmented actinic keratosis.


Clods

Clods + structureless: combined symmetrically or asymmetrically.

Symmetrical pattern

Structureless zone in the center of the lesion and clods at the periphery.

Skin-colored center "SuperficialThis glossary term has not yet been described. and deep" congenital nevus, Spitz nevusThis glossary term has not yet been described..

Brown or black center Growing "superficial and deep" congenital nevus (commonly in children), pigmented Spitz nevus.

Blue structureless center Combined congenital nevus.


Asymmetrical pattern

Contains clods but no lines. Pseudopods or circles are analyzed depending on whether the colors are predominantly those of melanin, or of another pigment.

Lesions pigmented by melanin They are predominantly black, brown, gray or blue.

Black pigmentation: coagulated blood or melanin. The interpretation depends on what other colors are present. Brown, blue or gray: melanin in the stratum corneum. Red or purple: coagulated blood.


Lesions with no pigment, or with pigments other than melanin They are assessed based on the color of the clods.

White or yellow clods: seborrheic keratosis. Orange clods: seborrheic keratosis, basal cell carcinoma. Red or purple clods: hemangioma, vascular malformation, melanoma or melanoma metastasis.


Melanin as predominant pigment The color of the whole lesion should be assessed:

Brown color: "superficial and deep" congenital nevus or a Spitz nevus. Other colors also present: basal cell carcinoma, melanoma, seborrheic keratosis and its variants. T


Dots

The algorithm for "dots and structureless" differs only slightly from the algorithm for "dots".

Gray dots: melanoma, lichen planus-like keratosis, pigmented superficial squamous cell carcinomaThis glossary term has not yet been described. (actinic keratosis or Bowen’s disease), basal cell carcinoma.

Blue dots: basal cell carcinoma.

Black dots: uncommon; exclude melanoma.

Brown dots: solar lentigo, pigmented Bowen’s disease, Clark nevus.