Skin nonmelanocytic tumor
Premalignant / in situ
Actinic keratosis

Topic Completed: 1 June 2012

Minor changes: 1 December 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Actinic keratosis [title]

Christopher S. Hale, M.D.
Page views in 2020: 27,770
Page views in 2021 to date: 5,998
Cite this page: Hale CS. Actinic keratosis. website. Accessed March 6th, 2021.
Definition / general
  • 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

  • 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
  • 54 year old man with inflammation of actinic keratosis due to alkylating agents for lung cancer (Cases J 2009 Jul 2;2:6946)
  • Curettage, cryotherapy, topical chemotherapeutic agents (Imiquimod, 5-FU)
Clinical images

Contributed by Ha Do, M.D.

Actinic keratosis

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

Images hosted on other servers:

Various images

Positive stains
Differential diagnosis
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