Actinic keratosis / Bowen's disease / keratoacanthoma / squamous cell carcinoma
| Subchapter(s): |
Squamous cell carcinoma
- 1 Introduction
- 2 Actinic Keratosis
- 3 Bowen’s disease
- 4 Keratoacanthoma
- 5 Squamous cell carcinoma
Actinic (solar) keratosis (AKThis glossary term has not yet been described.), Bowenalso known as squamous cell carcinoma in situ 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 malignantThis glossary term has not yet been described. 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 patterns 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 specificity. 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 dermoscopyDermoscopy is a non invasive diagnostic method., 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 immersion medium, such as ultrasound gel, when applying contact dermoscopy eliminates the effect of pressure-induced compression of blood vessels.
Actinic keratoses (AKs) typically arise on chronically sun-damaged skin and represent the most common lesions in the spectrum of keratinocyte skin cancer. 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. 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.
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 sensitivity 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 Network 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)
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 flat melanocytic lesions inflammatory diseases Bowen disease (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. While BCC has a very low metastatic risk, this tumor can cause significant disfigurement by invading surrounding tissues (BCCThis glossary term has not yet been described.) 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 are most commonly having a rough texrure with scaly-appearing surface and sharp border.
The reported dermoscopic characteristics of the pAK include:
- Evident follicles: Hair follicle openings of different sizes.
- White circles: White ring-like structures 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 help 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.
Bowen’s disease 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 presentation is an erythematous scaly patch or slightly elevated plaue.
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
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.
- 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.
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 papulonodular, plaque-like, papilomatous or exophytic.
- 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.
- 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 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.
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