Squamous cell carcinoma of the oral cavity originates from which epithelial cell layer?

Squamous cell carcinoma (SCC) originates from the basal layer (stratum basale) of the stratified squamous epithelium. The basal cells are the proliferating stem cells of the epithelium, and malignant transformation occurs in these actively dividing cells. Histologically, SCC shows invasion of atypical squamous cells beyond the basement membrane into the underlying connective tissue. The stratum spinosum contains differentiated squamous cells; while these are the 'squamous' cells giving the carcinoma its name, the tumor originates from the basal/parabasal region where cell proliferation occurs. Basal cell carcinoma, a different tumor, derives from the basal cells of the skin (not common in the oral cavity).