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Skin - Nonmelanocytic tumors

Premalignant or noninvasive

Actinic keratosis

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 7 May 2014, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● 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

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

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

Case reports

● 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

Solar (actinic) keratosis - various images

Contributed by: Dr. Ha Do (IUPUI)

Gross description

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

Micro description

● 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

Various images

Positive stains

● p53 (75%)

Differential diagnosis

● Superficially invasive squamous cell carcinoma

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

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