Revised two-step algorithm

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Main PageTwo-step algorithmRevised two-step algorithm
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 Authored by: Ashfaq A. Marghoob     ·  Aimilios Lallas     ·  Ralph P. Braun

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Author(s) Ashfaq A. Marghoob · Aimilios Lallas · Ralph P. Braun
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Status update November 12, 2017
Status by Ralph P. Braun
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The top-down 2-step pattern analysis approach builds upon the previous 2-step approach by eliminating the requirement to differentiate melanocyticThis glossary term has not yet been described. from non-melanocytic lesions in step 1. This 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. hinges on the concept that the observer’s diagnostic accuracy for skin cancer, specifically melanomaThis glossary term has not yet been described., is, metaphorically, like a two sided coin. One side of the coin requires the observer to make a specific diagnosisThis glossary term has not yet been described. by recognizing the classic patterns/structures associated with neviThis glossary term has not yet been described., dermatofibromas (DF), intradermal nevi (IDN), basal cell carcinomas (BCC), squamous cell carcinomas (SCC), lentigines & seborrheic keratosesThis glossary term has not yet been described. (SK), angiomas, angiokeratomas, sebaceous hyperplasias, and clear cell acanthomaThis glossary term has not yet been described. (CCA). Needless to say, the individual dermoscopic structures present in a lesion, within each diagnostic category (nevusThis glossary term has not yet been described., DF, BCC, etc), need to be placed within the context of the other features within the lesion. In other words, the global pattern defining a specific diagnosis is defined by the presence of distinct structures that have previously been found to carry a high predictive value for that specific diagnosis.

The other side of the coin requires the observer to acknowledge the nevus patterns that require context for their interpretation and the patterns and structures associated with melanoma. Armed with a clinical differential diagnosis followed by evaluation of the lesion via this top-down 2-step approach can facilitate the rendering of an accurate diagnosis or at least guide the clinician towards the most appropriate managementThis glossary term has not yet been described. plan.

Step 1:

Level 1: The most common patterns found in nevi (excluding IDN).

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Network or reticular patternA lesion with a reticular pattern has typical pigment network throughout the entire lesion.:

consists of an organized network with minimal variation in its thickness 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. (i.e., regular/typical networkNetwork with minimal variability in the color thickness and spacing of the lines; symmetrically distributed). The holes of the network are relatively uniform in their appearance.

Patchy network/reticular pattern:

patches of typical network distributed in an organized manner. The network patches all have the same type of network with minimal variability in the thickness and color of the linesstreaks. It is important to remember that melanoma on sun damaged skinThis glossary term has not yet been described. can sometimes appear as an isolated large lentiginous lesion with a patchy network. The cluesThis glossary term has not yet been described. to the diagnosis include the ageprocess of becoming older of the patient since these melanomas occur in the elderly, the network is usually not distributed in an organized fashion, and there is usually focal granularityThis glossary term has not yet been described. present.

Peripheral network with central hypopigmentation:

The peripheral network is typical/regular and the central hypopigmented area is lighter in color compared to the network but darker than the surrounding skinThis glossary term has not yet been described..

Peripheral network with central hyperpigmentation.

The peripheral network is typical/regular and the central hyperpigmented area consists of a blotchDark structureless areas. This blotch often due to the accumulation of melanin laden corneocytes in the straum corneum (i.e., lamella). This lamella can usually be tape stripped off revealing an underlying typical network.

Peripheral network with central brown globulesThis glossary term has not yet been described.:

The peripheral network is typical/regular and the central brown globules are also regular displaying minimal variation in their size and color.

Globular patternThis glossary term has not yet been described.:

This pattern consists only of globules that display minimal variability in their sizes and colors (i.e., regular/typical) and are distributed in an organized manner within the lesion. The globules can have different shades of brown. On rare occasion the globules can be white as seen on balloon cell nevi. While black and blue globules can on occasion be seen in congenital neviThis glossary term has not yet been described., their presence should raise suspicion for melanoma.

Cobblestone globular patternThis glossary term has not yet been described.:

This is a specific type of globular pattern that consists of large brown angulated globules that create a pattern reminiscent of cobblestones. This is a pattern associated with congenital nevi.

Reticular patternA lesion with a reticular pattern has typical pigment network throughout the entire lesion. with peripheral globulesThis glossary term has not yet been described.:

This pattern consists of a typical network nevus that has a peripheral rim of regular brown globules. This pattern is associated with the radial growth phase of Clark’s/dysplastic neviThis glossary term has not yet been described. and is commonly encountered in younger patients with the atypical mole syndrome.

Homogeneous blue:

A homogeneous blue color with a whitish veil that encompasses the entire lesion’s surface is the hallmark of a blue nevusThis glossary term has not yet been described.. The blue color and white veil in blue nevi will have minimal variation in hues. If there are multiple hues (i.e, heterogeneous blue color or non-homogeneous veil) then one should consider the diagnosis of melanoma. In addition, the differential for blue nevi should include epidemiologic metastasis and if nodular then one needs to consider the diagnosis of nodular melanomaThis glossary term has not yet been described..

Homogeneous brown:

This pattern consists of a nevus with homogeneous brown color with minimal to no variation in its hues. While it is usually devoid of any other structures, on rare occasions one can see a few regular dotsDots clustered at the center of the lesion, or located on the network lines (also called target network)/globules and fragments of network. This pattern is seen in congenital nevi.

Level 2: Dermatofibromas

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are defined first and foremost by their clinical characteristics of being firm papules that dimple on later pressure. A DF with this clinical morphologyThis glossary term has not yet been described. will usually reveal the following features when viewed with dermoscopyDermoscopy is a non invasive diagnostic method.: A symmetric lesion with a thin, typical, peripheral network with a central white scar-like area. In the region between the network and the central scarlike area one can see ring like globules and vesselsThis glossary term has not yet been described.. When viewed with polarized lightThis glossary term has not yet been described. the central scarlike area will usually manifests a pink hue and will often also reveal shiny white lines.

Level 3: Intradermal nevi

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are first and foremost defined by their clinical morphology as either raised dome shaped lesions or as sessile mamillated lesions. IDN with this clinical morphology will usually reveal one or more of the following features: comma vesselslinear curved short vessels dermal nevi, brown halo, globules, small foci of tan structureless pigmentation, hypopigmented areas. They can also reveal arborizing vesselsanalytic term is branched vessels; Bright red sharply in focus large or thick diameter vessels dividing into smaller vessels; BCC making it difficultThis glossary term has not yet been described. to differentiate them from BCC. The clues to the diagnosis of IDN include the presence of the aforementioned features and lack of other BCC-specific features. In addition, the arborizing vessels in BCC are often a tad out of focus and have a bluish hue. In contrast, in BCC the arborizing vessels are sharply in focus and bright red in color.

Level 4: BCC: Features associated with BCC: (see chapter on BCC for definitions)

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  • Arborizing (branched) vessels
  • Spoke wheel structures
  • Leaf like areasThis glossary term has not yet been described.
  • Blue gray ovoid nestWell-circumscribed ovoid structures with confluent or near confluent blue-gray pigmentation.
  • Blue gray non-aggregated globules
  • Multiple blue gray dots distributed in a buckshot scatter
  • Shiny white blotches and strandsWhite structures in the form of circles, oval structures, or large structureless areas that are bright-white longer and less well defined lines oriented parallel or distributed haphazardly, or forming blotches (shiny white clods). Seen only under polarized dermoscopy.
  • Ulceration

Level 5: SCC: Features associated with SCC: (see chapter on SCC for definitions)

Scale (rough texture) is present in almost all lesions
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  • Glomerular (coiled) vessels
  • Focally distributed towards the periphery
  • Diffusely present throughout lesion
  • Aligned linearly within lesion
  • White circles
  • Brown circles
  • RosettesFour bright white dots or clods arranged together as a square (or a four leaf clover) (seen with polarized light)
  • Brown dots aligned in a linear fashion
  • Strawberry patternReddish pseudo-network (erythema and wavy fine vessels) around hair follicle openings which are accentuated with a white halo appearance seen in 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. (AK)
  • Hairpin (looped) vessels with a white halo can be seen in keratoacanthomas (KA). In KA these looped vesselsmetaphoric term: hairpin vessels <br />

two parallel linear vessels forming a half looped or hairpin like structure <br /> seen in seborrheic keratosis viral warts tend to be aligned at the periphery.

Level 6: SK & lentigo: Features associated with SK and lentigo: (see chapter on SK for definitions)

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  • Moth eaten borders
  • Sharp boarders
  • Fingerprint like structuresThis glossary term has not yet been described.
  • Multi milia like cysts & comedo like openings
  • Gyri and sulci (cryptsKeratin filled invaginations that are larger than comedo- like openings Moth eaten border Border with concave or sharp punched-out invaginations) creating a cribriform pattern
  • Hairpin (looped) vessels with a white halo

    Level 7: angiomangiomas are benign tumors derived from cells of the vascular or lymphatic vessel walls (endothelium) or derived from cells of the tissues surrounding these vessels.[1][2] Angiomas are a frequent occurrence as patients age, but they might be an indicator of systemic problems such as liver disease. They are not commonly associated with malignancy./angiokeratomaThis glossary term has not yet been described./hemangioma

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  • Angioma and hemangiomas: lacunaeThis glossary term has not yet been described. with red to maroon to bluish colors that are separated from each other with intervening stroma.
  • Angiokeratomas: lacunae with varying shades of red, maroon and bluish. In addition ,there are thrombosed lacunae that have a black color. The center of the lesion often has a blue-whitish veil and the surrounding skin has an erythematous halo.

Level 8: Sebaceous hyperplasiaThis glossary term has not yet been described.

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These are small papules that reveal whitish/yellowish globules resembling pop-corn like structures. Crown vesselsRadial 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 are also seen. These vessels are present at the periphery. They radiate towards the center but do not cross its midline. Molluscum contagiosumThis glossary term has not yet been described. will manifest a similar pattern.

Level 9: Clear cell acanthomaThis glossary term has not yet been described.

these lesions will reveal vessels, including dotted or glomerular, arranged in a string of pearlsCoiled or dotted vessels arranged in lines clear cell acanthoma pattern.

Step 2

If a specific diagnosis cannot be rendered then the observer moves to the second step of the algorithm. The second step requires evaluation of a group of nevi that demand special attention since the context will dictate management. The second step also involves evaluating lesions for the presence or absence of melanoma specific patterns and structures.

NeviThis glossary term has not yet been described. requiring special consideration:

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  • The two component pattern and the multi-component symmetric pattern are commonly encountered in patients with the atypical mole syndrome. However, if it is an outlier lesion compared with the patient’s other nevi then one should consider a biopsy or close digital monitoring to ensure stability.
  • The homogeneous tan to pink nevus is a common pattern seen in nevi in individuals with type I-II skin. However, this pattern can also be seen in amelanotic and hypomelanotic melanomas. Thus, if such lesions appear to be outliers, caution should be exercised.
  • The tiered peripheral globular pattern is associated with nevi having a spitzoid morphology on dermoscopy. While the management of spitzoid lesions remains controversial, if such a lesion develops in older age, then one should consider a biopsy.
  • The typical starburst patternThis pattern consists of peripheral globules, pseudopods or streaks (or a combination of them), located around the entire perimeter of the lesion is associated with Reed’s nevi. While this is usually a benignThis glossary term has not yet been described. pattern, on rare occasions melanoma can masquerade itself as a starburst pattern lesion. Thus, a classic starburst pattern in individuals under the age of 12 can be monitored, however, such lesion in older individuals should be viewed with suspicion.

MelanomaThis glossary term has not yet been described. patterns:

Melanomas will usually manifest a disorganized distribution of structures and colors making their identification quite easy. These lesions will reveal at least one, but usually more than one, of the melanoma specific structures listed below. On rare occasions melanomas will present with a symmetric and organized pattern but these tumors will almost always reveal one of the following features: starburst pattern, negative networkSerpiginous interconnecting broadened hypopigmented lines that surround elongated and curvilinear globules., blue-black or gray color, shiny white structures, vessels or ulceration.

A few melanoma patterns deserve special mention.
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  • Featureless or structureless (non-specific or feature poor) lesions are lesions that have no dermoscopic structures or do have dermoscopic structures but the structures present cannot be used to differentiate benign from malignantThis glossary term has not yet been described.. If such lesions are non-palpable then they can be digitally monitored or can be biopsied. If such a lesion is palpable then digital monitoring is contraindicated and the lesion should be biopsied.
  • Melanoma should be in the differential diagnosis for any blue-black nodule.
  • Melanoma in situThis glossary term has not yet been described. can manifest a pattern comprised of small foci of hyperpigmentation. The hyperpigmented areas differ from blotches in that they are small (cover <10% surface area), multiple and do not obscure the ability to see underlying structures. These melanomas will also often reveal prominent skin markings.
  • Melanoma on sun damaged non-facial skin (lentigo malignaThis glossary term has not yet been described.) is associated with the following patterns: patches of peripheral network islands, tan structureless areas with granularity, and a lesion with angulated lines.

Melanoma specific structures:

Structures

Almost all melanomas will reveal at least one of the following structures/features:

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  • Atypical networkNetwork with increased variability in the color, thickness, and spacing of the lines of the network; asymmetrically distributed; gray color

Typical networkNetwork with minimal variability in the color thickness and spacing of the lines; symmetrically distributed consists of brown lines with minimal variability in their color and thickness. The holes of the network are of similar size. Atypical network consists of lines with increased variability in color and thickness. The atypical lines are often broadened, smudgy in appearance and often have a grayish color.

  • Angulated lines
  • Negative networkSerpiginous interconnecting broadened hypopigmented lines that surround elongated and curvilinear globules.
  • Atypical streakslines, radial (always at periphery) Reed nevus, melanoma, recurrent nevus

Typical streaks consist of streaks arranged symmetrically around the entire perimeter of the lesion as seen in Reed’s nevi.
Atypical streaks consist of streaks that are only focally present at the periphery.

  • Atypical dots and globules

Typical dots consist of dots that are centrally located within an otherwise organized lesion or dots associated with a typical network. The typical dost associated with a typical network are located on the network lines on in the holes of the network. Any other manifestation of dots is considered atypical.
Atypical dots are distributed asymmetrically, are not clustered in the center and are associated with an atypical networkNetwork with increased variability in the color, thickness, and spacing of the lines of the network; asymmetrically distributed; gray color. Typical globules are those found in nevi described in step-1 of this algorithm. Globules of similar shape, size and color distributed throughout the lesion (including cobblestone), at the periphery of an otherwise reticular nevus, or in the center of an otherwise reticular pattern nevus are considered typical.
Any other manifestation of globules would be considered atypical.

  • Peripheral tan structureless areas
  • Atypical blotches

Typical blotch consists of one round to oval homogeneous blotch in the center of an otherwise reticular pattern nevus.
Atypical blotch consists of an off center blotch or the presence of multiple blotches. The blotches can have irregular shapes and hues.

  • Multiple small hyperpigmented areas in a lesion with accentuated skin markings
  • Blue-white veil over raised areas
  • RegressionThis glossary term has not yet been described. structures (flat, non-palpable areas)
  • GranularityThis glossary term has not yet been described. / peppering
  • Scar lie depigmentation
  • Blue-white veil over flat area
  • Shiny white lines

Atypical vessels

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  • Comma vesselslinear curved short vessels dermal nevi in flat lesions (not IDN)
  • Dotted vesselstiny pinpoint vessels flat melanocytic lesions inflammatory diseases Bowen disease
  • Serpentine or linear vesselsLinear mildly curved vessels considered irregular when different sizes shapes and curves with a haphazard or random distribution are presented and considered regular when short and fine (thin) linear vessels prevail various diagnoses
  • Milky red areasMilky-white appearance or pinkish structureless areas ("strawberry and ice cream"-like), consisting a red vascular blush with no specific distinguishable vessels and globules
  • Polymorphous pattern. The most common pattern is one with both dotted and serpentine vesselslinear irregular linear vessels with multiple bends flat BCC melanoma
  • Corkscrew vesselstwisted looped vessels with bends twisted along a central axis melanoma metastasis

    Melanoma patterns on Special sites: (see specific chapters for details)

Volar: melanomas on the palmsThis glossary term has not yet been described. and solesThis glossary term has not yet been described.

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  • Parallel ridge patternVolar pigmentation forming lines, parallel, diffuse and irregular, along the ridges or cristae superficiales (raised portion of the dermatoglyphics)
  • Atypical fibrillar patternLinear pigmented filamentous lines of similar length with one end at the furrows and oriented at a certain angle to the furrows and crossing the ridges
  • Diffuse pigmentation with multiple shades of brown
  • Multi-component pattern

FaceThis glossary term has not yet been described.

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  • Annular-granular pattern
  • Asymmetric follicular openings
  • Gray dotsThis glossary term has not yet been described./granules around ostial openings
  • Circle within circle sign
  • Angulated lines forming rhomboidsGray-brown angulated lines forming a polygonal shape around adnexal ostial openings.
  • Blotches

Nails:

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The presence of melanin inclusions defines the lesion as melanocytic. These lesions consist of melanocyte activation as seen in lentigo or melanocytic proliferation as seen in nevi and melanoma. While evaluating the nailThis glossary term has not yet been described. plate it is important not to overlook evaluating the paronychia (micro-Hutchinson’s sign) area and hyponychial skin (parallel ridge patternVolar pigmentation forming lines, parallel, diffuse and irregular, along the ridges or cristae superficiales (raised portion of the dermatoglyphics) will be seen).

  • Atypical bands
consisting of lines of different colors and thicknesses. The bands may lose their parallelism and appear to converge distally creating a triangular appearance to the band (wider at proximal end and narrow at the distal end)

Mucosa:

The features to define early mucosal melanoma have not yet been elucidated. Clearly any lesion with a multi-component pattern should be viewed with suspicion. In addition, any lesion manifesting the colors blue, gray or white should be view with concern for melanoma.