Actinic keratosis / Bowen's disease / keratoacanthoma / squamous cell carcinoma

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Main PageNon melanocytic lesionsActinic keratosis / Bowen's disease / keratoacanthoma / squamous cell carcinomaActinic keratosis
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Introduction

Actinic (solar) keratosis (AKThis glossary term has not yet been described.), 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 (BD), keratoacanthomaThis glossary term has not yet been described. (KA), and squamous cell carcinomaThis glossary term has not yet been described. (SCCThis glossary term has not yet been described.) comprise the spectrum of premalignant and malignant keratinizing tumors. In contrast to the well-defined dermoscopic criteriameasure of how well one variable or set of variables predicts an outcome of pigmented tumors, the dermoscopic features of these, mostly non-pigmentedThis glossary term has not yet been described. keratinizing tumors, are less well established. Most of the described dermoscopic patternsThis glossary term has not yet been described. are based on case series. The dermoscopic 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 these tumors is mainly based on the assessment of vascular patterns. The architectural arrangementThis glossary term has not yet been described. and distribution of the vesselsThis glossary term has not yet been described. within the lesion and the correlation with the clinical assessment (e.g. texture, firmness) may provide improved specificityThis glossary term has not yet been described.. Other associated, but nonspecific features are erythema, scale, erosion or keratin. Since their diagnosis is mostly based on the ability to visualize blood vesselsare the part of the circulatory system, and microcirculation, that transports blood throughout the human body under 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., the use of polarized lightThis glossary term has not yet been described. dermoscopy instruments seems to provide the best method to visualize vascular structuresThis glossary term has not yet been described.. On the other hand, using a viscous immersionThis glossary term has not yet been described. medium, such as ultrasound gel, when applying contact dermoscopy eliminates the effect of pressure-induced compression of blood vessels.

Actinic Keratosis

Actinic keratoses (AKs) typically arise on chronically sun-damaged skin and represent the most common lesions in the spectrum of keratinocyte skin cancerThis glossary term has not yet been described.. Clinically they present as multiple pink macules or papules with a variably scaly surface.

Nonpigmented actinic keratosisActinic keratosis (also called solar keratosis and senile keratosis; abbreviated as AK) is a pre-cancerous patch of thick, scaly, or crusty skin.

Nonpigmented AK on the faceis a central body region of sense and is also very central in the expression of emotion among humans and among numerous other species. show four dermoscopic features, allowing an accurate diagnosis with high sensitivityThis glossary term has not yet been described. and specificity:

  • Erythema: Structureless pale-red Areas without any recognizable areas of hypopigmentation
  • Pink-to-Red pseudonetworkA structureless pigment area interrupted by non-pigmented adnexal openings: structureless red areas that resemble NetworkThis glossary term has not yet been described. structure- small white areas correspond to follicular openings of the skin
  • Fine, wavy vessels (straight or coiled) surrounding the hair follicles
  • Targetoid hair follicles: Hair follicle openings surrounded by a white halo and filled with a yellowish keratotic plug (white circle surrounding a yellow clod)

    Actinic keratosisActinic keratosis (also called solar keratosis and senile keratosis; abbreviated as AK) is a pre-cancerous patch of thick, scaly, or crusty skin. demonstrating targetoid hair follicles and diffuse erythema


On nonfacial skinThis glossary term has not yet been described., AK usually exhibits nonspecific patterns, with features such as surface scale and keratin and dotted vesselstiny pinpoint vessels (tiny red dots densely aligned next to each other).

An additional clue to the diagnosis of AK is the rosette sign, which can only be seen with polarized light and consists of a white four-leaf clover-shaped structure. Although the rosette sign can be seen in actinic damaged skin and in tumors such as 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 (BCCAbbreviation for Basal Cell Carcinoma) and melanomaThis glossary term has not yet been described., they are more commonly encountered in AK and thin SCCs.

Pigmented actinic keratosis

Pigmented variants of AK (pAK) mostly occur in darker skin phototypes. The discrimination between benignis any condition that is harmless in the long run pAK and pigmented tumors such as Lentigo maligna (LMThis glossary term has not yet been described.) may be challenging, due to the dermoscopic overlapping morphological features. The clinical differentiation from LM may be possible through palpation; pAK most commonly have a rough texture with scaly-appearing surface and sharp borders.

The reported dermoscopic characteristics of pAK include:

  • Evident follicles: Hair follicle openings of different sizes.
  • White circlesThis glossary term has not yet been described.: White ring-like structuresThis glossary term has not yet been described. within the hair follicle. The follicle may have a targetoid appearance with central yellowish keratotic plug surrounded by a white halo
  • Grey rhomboidal structures: Grey confluent dots arranged in lines or grey-to-brown linear structures located between follicular structures

The dermoscopic differential diagnosis of pAK is supported by the presence of a prominent pseudonetwork located between keratin-filled ostial openings. The dermoscopy of LM may on the other side reveal asymmetrical pigmented follicular openings and a darker dotSee [[Glossary:Dots|Dots]] located within ostial openings (some call this the isobar sign); a finding rarely seen in pAK.

The dermoscopy may helpRefers to giving assistance or support to others for mutual benefit guide the best location to biopsy. Biopsying areas which reveal the most suspicious features, such as annular–granular structures, asymmetric follicular openings, dots within the ostial openings, or rhomboidal structures may provide an accuse histologic diagnosis.

Pigmented actinic keratosis
Pseudo networkThis glossary term has not yet been described. in pigmented actinic keratosis

Bowen’s disease

Non-pigmentedThis glossary term has not yet been described. Bowen’s disease

Bowen’s disease (BD) represents an intraepithelial carcinoma or in situThis glossary term has not yet been described. Squamous cell carcinomaThis glossary term has not yet been described. (SCC). The most frequent clinical presentationThis glossary term has not yet been described. is an erythematous scaly patch or slightly elevated plaque.

The archetypal dermoscopic pattern of BD is characterized by two types of vascular patterns:

  • Clustered vascular pattern: Focal, clustered, asymmetric distribution of the vessels
  • Glomerular (coiled) vessels: Tortuous capillaries, which are larger than dotted vessels and are often distributed in clusters mimicking the glomerular apparatus of the kidney

The concurrent presence of hyperkeratosis (surface scale) allows a high diagnostic probability

Pigmented Bowen’s disease

Pigmented Bowen’s disease (pBD) is more frequently described in darker skin phenotypes.

The following dermoscopic criteria are suggested to be a specific clue for the diagnosis of pBD:

  • Brown or grey 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).: these dots are a strong clue when arranged as linear radial lines at the periphery of the lesion
  • Pink or skin colored eccentric structureless areahomogenous pattern various diagnoses


KeratoacanthomaThis glossary term has not yet been described.

Keratoacanthoma is a well-differentiated variant of Squamous cell carcinoma. Clinically, it is distinguished by its initial rapid growth followed by spontaneous involutionThis glossary term has not yet been described. over a period of a few months.

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. criteria:

  • White circles: White ring-like structures within the hair follicle
  • Keratin mass: Centrally located, amorphous, yellow-white to light brown areas without any recognizable structure
  • White structureless areas: Absence of any structure; they may be associated with large targetoid hair follicles

The central keratin plug is an architectural criterion for the diagnosis of keratoacanthoma also on the histopathological analysis and may be typically surrounded by elongated and sometimes thick telangiectasias.


Keratoacanthoma schematic.jpg

Keratoacanthoma.jpg

Vascular architecture of Keratoacanthoma

  • Hairpin vessels: Vascular Loops frequently twisted and bending, usually surrounded by whitish halo
  • Linear-irregular vessels: Serpentine or branched Serpentine; irregularly shaped, sized and distributed red structures
  • Glomerular (coiled) vessels: Larger than dotted vessels with convoluted morphologyThis glossary term has not yet been described. and often distributed in clusters

Squamous cell carcinoma

Squamous cell carcinoma (SCC) is the second most common cutaneous malignancy after Basal Cell Carcinoma with an increasing incidence worldwide. It usually arises on sun-exposed areas of the skin, such as scalp, face, neck, forearms and dorsal hands.

Invasive squamous cell carcinoma

Invasive SCC appears often clinically as a papulonodular, plaque-like, papilomatous or exophytic lesion.

Dermoscopy criteria

  • Central mass of keratin: amorphous, yellow-white to light-brown areas without any recognizable structure
  • Targetoid hair follicles: keratotic plugs within follicular openings of the skin, mostly over a white structureless area
  • Ulceration: large irregularly shaped or roundish areas of dull red or red-brown structureless 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.

Vascular architecture

  • Herpin vessels: vascular loops, usually surrounded by whitish halo
  • Linear-irregular vessels (serpentine): linear or slightly curved, irregularly shaped, sized and distributed red structures

Other vascular patterns, such as dotted and glomerular (coiled) vessels may also be present. Combinations of these vascular morphologies result in the so-called polymorphous pattern.

Poorly differentiated SCCs are dermoscopically typified by a predominantly red color, resulting from the presence of bleeding and dense vascularity. On the other hand, white colored criteria (central mass of keratin, whitish halos and structureless whitish areas) are associated with well- or moderately differentiated variants.

Progression model of actinic keratosis to squamous cell carcinoma

Invasive SCC often arises in association with actinic keratosis (AK). The progression model of AK to SCC suggests an initial transition from a red pseudonetwork ("strawberry patternReddish pseudo-network (erythema and wavy fine vessels) around hair follicle openings which are accentuated with a white halo appearance") to an increasing neovascularization (development of clustered dotted/glomerular vesselsThis glossary term has not yet been described.). The follicles gradually miniaturize and disappear, whereas hairpin and linear-irregular vessels appear. Along with these vascular changes, a central mass of keratin forms and ulceration may occur.

Pigmented invasive squamous cell carcinoma

Pigmented invasive SCC is a rare variant of SCC. Dermoscopically, it reveals a diffuse, homogeneous blue pigmentation with distinct, irregularly distributed, blue-gray granular structures. If ulcerated, dark brown to black crusts are visible. Due to the pigmentation, vessels are usually not seen.




ReferencesThis is material contained in a footnote or bibliography holding further information.

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