Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

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Wednesday, September 20, 2006

What is an actinic keratosis of the eyelid?

Actinic Keratosis (Solar Keratosis)
Definition: a premalignant condition characterized by dysplasia of the basal cell layer of the skin.
Incidence/Prevalence: Prevalence for actinic keratosis of the skin in general ranges from 0.3% of the general population in Italy to about 3% in patients over 40 in Germany.
Etiology: Ultraviolet radiation induced oxidative damage is the predominant current etiologic hypothesis. Actinic keratosis as the name suggests is related to solar exposure.
Clinical Findings: Actinic keratoses range from millimeters up to 1 cm in size. They usually present as erythematous, scaly macules or papules in middle age on sun-exposed skin. Frequently the keratosis, or an elevated white flaky crust is seen on the surface.

Histopathology: The sine qua non for diagnosis in actinic keratosis is the presence of dysplasia of the basal cell layer of the epidermis. Accompanying architectural features include cellular and nuclear crowding with alteration of the polarity or maturation of the cells; cells fail to flatten at the higher layers of the epithelium. Cytologic findings include nuclear enlargement, nuclear hyperchromasia, nuclear membrane irregularity, mitotic figures, and increased nuclear-to-cytoplasmic ratios. Nuclear changes in actinic keratosis range from mild (involving only the basal epithelial layers) to frank carcinoma in situ, or full-thickness involvement of the epidermis. The underlying dermis shows solar elastosis (fragmentation, clumping, and loss of eosinophilia) of dermal collagen and a lichenoid chronic inflammatory infiltrate of varying intensity. Several subtypes have been described with the following features:
acantholytic- clefts in the epithelium above the atypical cells in the basal layer
atrophic- minimal hyperkeratosis, loss of rete ridges, a single layer of atypical basal cells
Bowenoid - carcinoma in situ; involves the entire epithelium
hypertrophic- hyperkeratosis, hypergranulosis, parakeratosis and papillomatosis.
In the figure below, one sees a typical actinic keratosis with downward budding or elongation

of rete pegs (arrows 1), atypia of the basal layer that extends along the rete pegs (arrows 2) acanthosis, marked hyperkeratosis, and parakeratosis (arrows 3). In addition there is a chronic inflammatory infiltrate at the base of the epidermis. Some of the enlarged and atypical basal cells extend along the adnexal structures as well.
pigmented type- melanin in the basal layer and dendritic cells within the epithelium, dermal pigment laden macrophages.
Treatment: Biopsy of suspicious lesions and follow-up are prudent in patients with this condition. The base of the lesion must be examined histopathologically to exclude invasive squamous cell carcinoma. Therefore, biopsies of suspected actinic keratoses should include the base of the lesion; shave biopsies should be avoided. Treatment alternatives include excision, cryotherapy and a variety of topical agents to extirpate the lesions.
Prognosis: Some authors state that in about 20% of patients with actinic keratoses, squamous carcinoma may develop in one or more of the lesions. However, when squamous cell carcinoma arises in actinic keratosis, the risk of subsequent metastatic dissemination is very low (0.5%-3.0%).

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