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Skin - Nonmelanocytic tumors

Premalignant or noninvasive

Actinic keratosis

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 4 July 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Also called solar keratosis, senile keratosis
● Buildup of excessive keratin due to chronic exposure to sunlight
● On sun-exposed sites (face, arms, dorsum of hands)
● Called actinic cheilitis in lips
● May become invasive with only a single layer of atypical keratinocytes

Risk factors:
● Fair skin, ionizing radiation, hydrocarbon or arsenic exposure, renal transplant

Treatment:
● Curettage, cryotherapy, topical chemotherapeutic agents (Imiquimod, 5-FU)

Variants:
● Acantholytic: lack of intercellular adhesion with clefts containing rounded, acantholytic cells
● Atrophic: epidermis has only 3-4 layers of keratinocytes
● Basaloid:
● Bowenoid: full thickness atypia
● Epidermolytic: vacuolar changes of keratinocytes at upper spinous and granular layers with coarse keratohyalin granules
● Hyperkeratotic: with cutaneous horn
● Pagetoid:
● Pigmented: resembles solar lentigo, which lacks atypia and has downward projections

Case reports
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● 54 year old man with inflammation of actinic keratosis due to alkylating agents for lung cancer (Cases J 2009 Jul 2;2:6946)

Clinical images
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Solar (actinic) keratosis - various images

Gross description
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● Tan-brown, red or skin colored, circumscribed lesions, sandpaper texture
● May have cutaneous horn (due to excessive production of parakeratotic scale)

Micro description
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● Basal cell and squamous layer atypia and disorderly maturation, hyperkeratosis, parakeratosis
● May have atrophy of epidermal surface
● Usually no granular layer except at follicular orifices
● Elastosis and often chronic inflammation of dermis
● Follicular apparatus and intraepidermal sweat duct are spared
● May have coexisting melanocytic atypia

Micro images
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Various images

Positive stains
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● p53 (75%)

Differential diagnosis
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● Superficially invasive squamous cell carcinoma

End of Skin - Nonmelanocytic tumors > Premalignant or noninvasive > Actinic keratosis

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