Actinic keratosis / Bowens's disease / 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.
Squamous cell carcinoma in situ / Bowen's disease
Bowen’s disease represents an intraepithelial carcinoma or in situ Squamous cell carcinoma (SCC). The most frequent clinical presentation is an erythematous scaly patch or slightly elevated plaque.
Non-pigmented Bowen's disease
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.
Figure: Bowen's disease with glomerular vessels and scales.
Pigmented Bowen's disease
- Brown or grey dots: these dots are a strong clue when arranged as linear radial lines at the periphery of the lesion
- Pink or skin colored eccentric structureless areas
- Glomerular (coiled) vessels, arranged randomly, as clusters, or in radial lines
Invasive squamous cell carcinoma
Invasive SCC appears often clinically as papulonodular, plaque-like, papillomatous or exophytic. Dermatoscopically, it is characterized by the presence of the following 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 color
- Hairpin 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 squamous cell carcinoma
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 pattern") to an increasing neovascularization (development of clustered dotted/glomerular vessels). 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.
Dermatoscopy has become an important bridge of communication between the dermatologist and the pathologist. Almost all dermatoscopic strucures have direct histopathologic correlates, as it can be observed it the image below. 
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