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 faceThis glossary term has not yet been described. show four dermoscopic features, allowing an accurate diagnosisThis glossary term has not yet been described. 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 vesselsThis glossary term has not yet been described. (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 skin, 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 lightThis glossary term has not yet been described. 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 (BCC) 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 benignThis glossary term has not yet been described. pAK and pigmented tumors such as Lentigo maligna (LM) 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 texture 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 dermoscopyDermoscopy is a non invasive diagnostic method. 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.
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