ABSTRACT
Actinic keratosis (AK), intraepidermal carcinoma, and squamous cell carcinoma (SCC) represent time-related stages in the progression of keratinocyte skin cancer, although SCC may also develop de novo. Clinically, three different grades of AK can be distinguished: grade I describes slightly palpable AK, grade II shows moderately thick AK, and grade III is very thick, hyperkeratotic, and/or clinically obvious AK. The most classical appearance of well-differentiated SCC of the keratoacanthoma type is that of a raised tumor showing a central mass of keratin intermingled with blood spots, which is surrounded by peripheral structureless white areas. The hallmarks of intraepidermal carcinoma are dotted or glomerular vessels that are typically arranged in small clusters or in radial lines. Glomerular vessels at 10-fold magnification appear as coiled vessels that are larger than the dotted vessels typically seen in melanocytic neoplasms. In contrast, poorly differentiated SCC commonly appears clinically as a flat ulcerated plaque and lacks dermoscopic signs of keratinization.
