Full-thickness keratinocytic atypia, often with prominent suprabasilar mitoses and apoptotic figures
• Squamous cell carcinoma (SCC)
Invasive islands of atypical keratinocytes involving stroma
Often associated with ulceration and dense inflammatory infiltrate
• Actinic cheilitis prurigo
Most common in Native Americans, usually presents in summer months after sun exposure
• Contact cheilitis
Similar to contact dermatitis, with spongiosis and eosinophils
• Plasma cell cheilitis
Clinical Photograph of Actinic Cheilitis This clinical photograph shows actinic cheilitis (AC) diffusely involving the lower lip with associated crusting . (Courtesy J. Wu, MD.)
Actinic Cheilitis Histologic Findings Histologic section of AC shows mucosal acanthosis with overlying parakeratosis. There is irregular budding and basilar atypia, with many of the cells showing enlarged, hyperchromatic-staining nuclei .
AC With Prominent Acanthosis AC with prominent mucosal acanthosis and elongation of the rete ridges is shown. Atypical keratinocytes involve the lower 1/3 of the epithelium, and scattered mitotic figures are easily identified .
Increased Ki-67 Staining in AC Immunohistochemistry for Ki-67 shows increased proliferative activity with strong nuclear staining in numerous basilar keratinocytes .
TERMINOLOGY
Abbreviations
• Actinic cheilitis (AC)
Synonyms
• Actinic keratosis (AK) of lip
• Solar cheilosis
• Cheilosis exfoliativa
Definitions
• Proliferation of atypical keratinocytes involving basilar layers of mucosal epithelium
• Minority of cases may transform into squamous cell carcinoma in situ (SCCis) or invasive squamous cell carcinoma (SCC)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
• Chronic sun exposure, especially UVB rays
• Smoking and chronic irritation are also risk factors
Infectious Agents
• Herpes virus infection and syphilis implicated in rare cases
CLINICAL ISSUES
Epidemiology
• Age
Occurs in older adults with longstanding solar damage
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. (Courtesy J. Wu, MD.)
and basilar atypia, with many of the cells showing enlarged, hyperchromatic-staining nuclei 
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