These cancers are also described based on how differentiated the cells are—well-differentiated, moderately differentiated and poorly differentiated . The less differentiated the lesion , the least amount of normal tissue is preserved and the more aggressive the cancer.
Verrucous carcinoma is a cauliflower-like (fungating) type of SCC found in the mouth, on the membranes lining the anus and genitals or on the bottom surface of the foot. There are also a number of lesions that are precancerous . Actinic keratoses, for example, are red, scaly discolored areas on sun-exposed areas of fair-skinned individuals that tend to scratch off but come back. Cutaneous horns are hard, funnel-shaped lesions extending from a red base on the skin. Also potentially precancerous is leukoplakia , a white patch on the oral and genital membranes.
How It Spreads Basal cell cancer usually remains unchanged for years or grows very slowly. It rarely spreads to distant sites. One study reported less than 0.01 percent occurrence of metastatic disease. The lesions that tended to spread were large, involved the head and neck with extensive local invasion and had recurred after treatment. When metastatic disease occurs it spreads to local lymph nodes and less often to bone, the lungs and the liver. Survival is less than one year once such spread has been discovered.
Squamous cell cancer has a higher rate of metastatic disease, with studies reporting a 3 percent rate of spread to distant sites. The most likely lesions to spread are large, invasive, greater than 4 mm (1/10 in.) thick and poorly differentiated.
