Misclassification of non-melanocytic lesions

From dermoscopedia

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 Editor: Ashfaq A. Marghoob

 Author(s): Ayelet Rishpon     ·  Ashfaq A. Marghoob
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Description this chapter describes the problems of classificationis a general process related to categorization, the process in which ideas and objects are recognized, differentiated, and understood. based on dermoscopyThe examination of [skin lesions] with a 'dermatoscope'. This traditionally consists of a magnifier (typically x10), a non-polarised light source, a transparent plate and a liquid medium between the instrument and the skin, and allows inspection of skin lesions unobstructed by skin surface reflections. Modern dermatoscopes dispense with the use of liquid medium and instead use polarised light to cancel out skin surface reflections. examination
Author(s) Ayelet Rishpon · Ashfaq A. Marghoob
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Status update July 20, 2018
Status by Ralph P. Braun


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Misclassification of non-melanocyticThis glossary term has not yet been described. lesions

Occasionally non-melanocytic lesions display a networkThis glossary term has not yet been described., globulesThis glossary term has not yet been described., streakslines radial (always at periphery) streaks Reed nevus melanoma recurrent nevus, or homogenous pigmentation potentially leading to the incorrect diagnosisis the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines with variations in the use of logic, analytics, and experience to determine "cause and effect". In systems engineering and computer science, it is typically used to determine the causes of symptoms, mitigations, and solutions of a melanocytic lesion.

Pigment networkGrid-like pattern consisting of interconnecting pigmented lines surrounding hypopigmented holes.

The reticular network reflects a pigmented basal layer, with its grid representing the pigmented rete ridgesEpidermal extensions that project into the underlying dermis and the holes representing the lesser pigmented suprapapillary plates. Whenever there is a corrugated and pigmented basal layer, whether its’ pigment lies within keratinocytes or within melanocytes, a corresponding reticular network appears on dermoscopy. Apart from melanocytic lesions, this structure could be seen in a solar lentigoThis glossary term has not yet been described., seborrheic keratosisThis glossary term has not yet been described., dermatofibromaDermatofibromas are hard solitary slow-growing papules (rounded bumps) that may appear in a variety of colours, usually brownish to tan; they are often elevated or pedunculated. A dermatofibroma is associated with the dimple sign; by applying lateral pressure, there is a central depression of the dermatofibroma. and accessory nipple.

Solar lentigoThis glossary term has not yet been described.

Solar lentiginesThis glossary term has not yet been described. not uncommonly display a reticular network. Differentiation from a melanocytic lesion is usually based on the network being regular, faint and delicate, demarcated with a sharp border or a moth-eaten borderThis glossary term has not yet been described., accompanied by the occasional presence of a clinical jelly sign fingerprintinglines brown curved parallel thin, milia-like cystsThis glossary term has not yet been described. and comedo-like openings[[Comedo like openings]]. A distinct type of lentigo is the ink-spot lentigo showing a unique dark brown thickened network that ends abruptly, commonly appearing following sun burns.

Seborrheic keratosisThis glossary term has not yet been described.

Pigmented seborrheic keratosesThis glossary term has not yet been described. occasionally demonstrate network-like structuresThis glossary term has not yet been described., typically in which the grid is thickened and the holes are wider than those formed by melanocytic lesions. The grid corresponds to ridgeThis glossary term has not yet been described. and the holes to the sulci or fissures. The grid can thicken to create a cerebriform appearance, formerly known as the “fat finger”. As with solar lentiginesThis glossary term has not yet been described., the network- like structuresThis glossary term has not yet been described. of seborrheic keratosis end abruptly. When there is a blue white veilBlue-white veil is confluent blue pigmentation with an overlying white “ground-glass” haze. In melanoma, the bluewhite veil does not occupy the entire surface area of the lesion, but rather is present as a focal, ill-defined area. Histopathologically, this dermoscopic structure corresponds to an aggregation of heavily pigmented cells (melanocytes and/or melanophages) or melanin in the dermis (blue color) in combination with compact orthokeratosis and linear irregularlinear vessels with multiple bends vesselsThis glossary term has not yet been described., the observer might mistake the lesion for a melanomaThis glossary term has not yet been described.. Gray granularityThis glossary term has not yet been described. observed in inflamed or regressed lesions might further add to the diagnostic difficulty.

DermatofibromaDermatofibromas are hard solitary slow-growing papules (rounded bumps) that may appear in a variety of colours, usually brownish to tan; they are often elevated or pedunculated. A dermatofibroma is associated with the dimple sign; by applying lateral pressure, there is a central depression of the dermatofibroma.

Dermatofibromas classically reveal on dermoscopy a delicate, tan-colored peripheral network, surrounding a central scar-like area. The delicate networklight brown, thin network lines corresponds to the “dirty feet” histologic appearance of the pigmented basal layer. At the inner edge of the network, circles are commonly seen, representing the widened rete ridges at the edges of the scar. The scar like area can display vessels, and under polarized lightThis glossary term has not yet been described. can show white lines overlying a pink background. As this pattern, along with a clinical dimple sign represent the prototype of dermatofibromas’ appearance, the two step algorithms specifically emphasizes it as an exception. Thus, when the above pattern is observed, a dermatofibroma can be diagnosed with certainty during the first step.


Supernumerary nipples

The areolar basal pigmentation of the nipple results in a dermoscopic delicate network, occasionally leads to the misdiagnosis as neviThis glossary term has not yet been described. or dermatofibromas. Diagnostic cluesEvidence, in an investigation for supernumerary nipples are their clinical appearance as soft papules present along the milk-line, typically with a stable history.


Supernumerary nipple.jpg

Dots and globules

Although dots and globules are commonly observed in melanocytic lesions, they can appear in a variety of non-melanocytic lesions, including dermatofibromas, seborrheic keratoses, pigmented Bowenalso known as squamous cell carcinoma in situ[1] is a neoplastic skin disease. It can be considered as an early stage or intraepidermal form of squamous cell carcinoma. It was named after John T. Bowen’s disease, basal cell carcinomas and cutaneous metastasis.

Dermatofibroma

As noted above, the inner edge of the network of dermatofibromas tends to show ring-like globular structure. This feature’s presence is probably related to the elongated rete ridges overlying the central scar-like area. A combinationThis glossary term has not yet been described. of clinical and dermoscopic clues including the dimple sign and central scar-like area featuring crystalline structures and occasional vessels are an aid to diagnosis.

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

The dermoscopy of pigmented basal cell carcinomas reflects the histologic pigmented tumor islands. Basal cell carcinomas can display and blue-gray non-aggregated globules and small and focused brown dots typically arranged in a “buckshot scatter” pattern. White shiny streaks, arborizing vesselsanalytic term is branched vessels; Bright red sharply in focus large or thick diameter vessels dividing into smaller vessels; BCC and a pink-white shiny background are suggestive of BCCAbbreviation for Basal Cell Carcinoma although they can appear on melanomas. That said, the misdiagnosis of a BCC as a melanoma would generally result in a similar, yet conceivably more rigorous managementThis glossary term has not yet been described. strategy.

BCC with globular structures.jpg
Seborrheic keratosis

Globules are not a common finding in seborrheic keratoses. However occasionally they are present, reflecting the epidermal pigmented horn cyst or comedo-like openings. The presence of a sharp border, ridges and sulci and milia-like-cysts are an aid to the correct diagnosis. A more challenging dermoscopic variant is the clonal seborrheic keratosis in which variable-sized pigmented globular structures are aggregated throughout the lesions, occasionally leading the observer to expand the differential diagnosis to include a melanoma or a BCC.

Clonal seb ker.jpg
Pigmented Bowen’s disease

Pigmented Bowen’s disease can display brown focal dotsDots are small, round structures of less than 0.1 mm in diameter that have a red color when corresponding to blood vessels; however, when due to melanin, their color ranges from black, brown, to blue-gray depending on the depth and concentration of the melanin in the skin (Tyndall effect)., often arranged in peripheral linear tracks {Cameron, 2010 #2342}. The presence of scale and dotted or glomerular vesselsThis glossary term has not yet been described. are an aid to the correct diagnosis.

Cutaneous metastasis

Tumors metastasizing to the skin can acquire melanin from epidermal melanocytes or become colonized with melanocytes leading to pigmented structures as irregular dotsAny distribution of dots other than dots as described for regular dots. and globuleThis glossary term has not yet been described., not uncommonly having the appearance of an atypical melanocytic lesion.

Pigmented streaks

Pigmented streaks are linear projections present at the periphery of the lesion. In melanocytic lesions they correspond to confluent junctional melanocytic proliferation but can be seen in variety of non-melanocytic lesions.

Seborrheic keratosesThis glossary term has not yet been described.

Seborrheic keratoses display pigmented bulbous rete ridge on histologyThis glossary term has not yet been described.. In the same manner as this histologic feature could reflect a thickened network when present in the center of the lesion, its’ present at the periphery could result in corresponding dermoscopic streak-like structures. In seborrheic keratoses the streaks tend to be thick and occasionally branched. This structure leads to the description of the starburst-like seborrheic keratosis. Clinically distinguishing the stuck-on lesions, those with a negative wobble signThis glossary term has not yet been described., and those that are featuring dermoscopic clues as milia like-cysts and comedo-like openingRound to oval keratin filled clefts facilitate the correct diagnosis.

SteaksSEB.jpg
seborrheic keratosis featuring peripheral streaks
This seborrheic keratosis has areas suggestive of streaks and an off center blotch. These features can lead to the false diagnosis of melanoma.
Basal cell carcinoma

BCC’s at times show thick streak- like structures arraigned radially, connecting to a common base. This is usually a variant of the leaf like structure of spoke-wheel structure.

StreaksBCCjpg.jpg
BCC featuring spoke wheels structures mimicking streaks
Pigmented Bowen’s disease

Irregular peripheral streaks corresponding to pigmented dendritic melanocytes are occasionally seen in pigmented Bowen’s disease, a rather rare variant of Bowen’s disease. Scale, ulceration and dotted or glomerular vessels are a clue to correct diagnosis.

Cutaneous metastasis

If epidermal melanocytes or melanin colonize skin metastasis at the periphery of the lesions, streaks could form in the same manner they are formed in melanocytic lesions.

Homogenous blue pigmentation

Due to Raleigh scattering, the shorter wavelengths (blue) are scattered, while the longer wavelengths (red) are mostly absorbed. Owed to this phenomenon, melanin and hemoglobin located deep in the dermis appear blue. Although the classic example of homogenous blue pigmentation is the blue nevusis a type of melanocytic nevus that clinically and dermoscopically will appear blue, this feature can appear in malignant melanocytic lesions (primary and metastatic melanoma) and in non-melanocytic lesions including Basal cell carcinomas, tattoos, cysts and vascular lesions.

Tattoos

Foreign material such as asphalt (traumatic tattoo) lead (pencil lead tattoo) or carbon ink (radiation tattoo) can create a homogenous blue lesion occasionally confused with a blue nevus. History is the main key to the correct diagnosis.

Basal cell carcinoma

Pigmented nodular BCC’s rarely appear as homogenous blue lesions. This feature, when present, probably results form a coalition of large ovoid nests.

Epidermal Cysts

Epidermal cysts occasionally have faint blue homogenous appearance. This results from the deeply located keratinous material covered by epithelial lining. Clinically the lesions generally feature as dermal bluish or yellowish nodules. The overlying epidermis occasionally features a punctum.

Vascular lesions

When angiomas and angiokeratomas are located deep in the dermis, occasionally the distinction between the vascular structuresThis glossary term has not yet been described. (lacunas) are not clear. Due to Rayleigh scattering these lesions can appear as homogenous blue or red blue lesions.

Dermatofibromas

Special variants of dermatofibromas such as hemosiderotic and aneurysmatic can display homogenous blue pigmentation due to hemosiderin deposition and large deep vascular channels. The dimple sign and a delicate peripheral network are an aid to the correct diagnosis.

Regression structuresThis glossary term has not yet been described.

Basal Cell Carcinoma

Regression structures and polymorphous vesselsmultiple types of vessels are present may indicate malignancy in appropriate context for example in flat melanocytic lesions usually speak in favor of melanoma but occasionally they can also be seen in BCCs as is the case in the image below.

Regression structures scc.JPG