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Syn: Solar Keratosis.
This lesion presents as multiple scaly
erythematous patches or cutaneous horns on sun-exposed areas in middle
aged and elderly patients.
Actinic keratosis may transform into squamous cell carcinoma if left
untreated.
Similar lesion on the lip is known as actinic cheilitis.
The clinical variants
include -
-Hyperplastic form which is commonly found on the hands.
-Spreading pigmented form which is usually found on the face.
Microscopic features:
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- Focal parakeratosis with loss of underlying granular layer.
- Loss of orderly arrangement of the epidermis . Large atypical
keratinocytes are present in the epidermis. This may vary from mild to
severe.
In bowenoid type actinic keratosis there is full thickness squamous atypia.
- Irregular bud like extension may be present in the papillary dermis.
This does not extend to the reticular dermis.
- The dysplastic changes are not present in the adnexal epithelium.
- Epidermolytic, pagetoid or pseudoglandular patterns may be noted.
- In the dermis there is prominent actinic elastosis and variable chronic
inflammatory cell infiltrate.
- Hypertrophic variant is characterized by psoriasiform hyperplasia,
orthokeratosis with alternating parakeratosis, mild dysplasia confined to
the basal cell layer.
- Pigmented variant displays melanin pigment in the keratinocytes and
melanophages.
- Lichenoid actinic keratosis is characterized by band like chronic
inflammatory cell infiltrate, apoptotic keratinocytes, vacuolar
degeneration of the basal cell layer together with parakeratosis of
stratum corneum and enlarged and atypical keratinocytes.
Differential diagnosis
includes superficial squamous cell carcinoma.
The following features favour squamous cell carcinoma-
- Presence of atypical keratinocytes in the reticular dermis.
- Independent nests of keratinocyte.
Pathologists should ask for step sections in
small biopsies suspected of actinic keratosis to rule out any invasive
component.
DermAtlas- Related link
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