Metastasis from the common squamous cell carcinoma arising in sun-damaged skin is rare. A vast majority appear to be only locally aggressive. Metastasis is more likely from carcinomas related to other antecedent lesions (burns, scars, chronic ulcers, arsenical dermatosis, x-ray injury) or of unknown etiology. Other characteristics of a dangerous lesion are large size great cellularity, and diffuse invasion. Other things being equal, the anaplastic tumor is probably more likely to metastasize and to metastasize more widely than the well-differentiated tumor.