What is a known precursor to squamous cell carcinoma?

• A. Basal cell carcinoma
• B. Actinic keratosis
• C. Squamous cell carcinoma
• D. Seborrheic keratosis

Answer: (B)

Actinic keratosis is a sun-induced dysplastic lesion of the epidermis that serves as a known precursor to squamous cell carcinoma. It arises from chronic UV damage causing atypical keratinocytes confined mainly to the epidermis, often presenting as a rough, scaly patch on sun-exposed skin. If these changes are not treated, the lesion can progress over time to invasive squamous cell carcinoma, especially with ongoing UV exposure or immune suppression. This makes actinic keratosis the best answer because it represents a premalignant state that can precede SCC.

Basal cell carcinoma is a distinct skin cancer with a different pathogenesis and does not typically serve as a precursor to squamous cell carcinoma. Seborrheic keratosis is a benign, non-pre-malignant lesion. Squamous cell carcinoma itself is the malignancy, not a precursor.