Review Question - QID 106752

Actinic keratoses as demonstrated in Figure E can progress to invasive squamous cell carcinoma.

Actinic keratosis (AK) is a premalignant lesion that is caused by sun exposure. They typically present as small, crusty, rough erythematous or brownish papules or plaques. AKs are considered to be pre-cancerous and if left untreated can progress to invasive squamous cell carcinoma (SCC) (Illustration A). According to one study, less than 0.1% of untreated AK lesions will progress to SCC over the course of one year, but annual rates of transformation have been as high as 20% in other studies. Diagnosis is made via biopsy, and standard treatment includes topical fluorouracil (5-FU), which acts by inhibiting methylation of thymidylate synthetase. This interrupts DNA and RNA synthesis.

McIntyre et al. review the diagnosis and treatment of actinic keratosis. They state that the decision to treat can be based on cosmetic reasons, symptom relief, or the prevention of malignancy. Treatment options include 5-fluorouracil and ablative therapies such as cryosurgery, curettage with electrosurgery, and photodynamic therapy.

Segatto et al. performed a randomized control trial to compare the efficacy of 3% diclofenac sodium and 5% 5-fluorouracil treatment for actinic keratosis. They found that 5-fluorouracil is more effective, but that it has a lower tolerability than diclofenac sodium.

Figures A-D are described in the incorrect answer choice explanations below. Figure F demonstrates acanthosis nigricans which is epidermal hyperplasia causing symmetrical, hyperpigmented, velvety skin and is commonly observed in diabetes and obesity. Illustration A demonstrates the clinical findings observed in SCC.

Incorrect Answers:
Answer 1: Figure A demonstrates seborrheic keratosis, a flat, greasy, pigmented squamous epithelial proliferation with keratin filled cysts. Seborrheic keratosis does not progress to SCC.
Answer 2: Figure B demonstrates psoriasis, silver scaling plaques and papules that are typically located on extensor surfaces such as knees and elbows. Psoriasis does not progress to SCC.
Answer 3: Figure C demonstrates atopic dermatitis (eczema), pruritic eruptions that commonly occur on flexural surfaces such as the antecubital fossa.
Answer 4: Figure D demonstrates erythema nodosum, inflammatory lesions of subcutaneous fat typically located on anterior shins. It is associated with sarcoidosis, coccidioidomycosis, histoplasmosis, and TB but is not associated with SCC.