Spatiotemporal Analysis of Molecular Continuity in Pathogenesis of Squamous Cell Carcinoma: From Normal Epithelium to Precancerous Lesions and Carcinoma.

Squamous cell carcinomas (SCCs) develop from the stratified epithelia of the esophagus, head and neck, lung, and skin, providing a tractable model to investigate how altered epithelial fields progress toward invasive cancer. Across SCC subtypes, evolution often begins before overt malignancy, with age- and exposure-associated mutant clones expanding within histologically normal epithelia. As lesions advance, early driver selection becomes coupled to copy number alterations, chromosomal instability, and epigenetic remodeling, whereas later stages are shaped by branching diversification, cellular plasticity, and regionally constrained selection. Despite tissue-specific differences, several recurrent principles emerge, including clonal expansion within mutated normal fields, transition bottlenecks marked by genome-scale instability, and the spatial organization of subclonal architecture and invasive-front states. In this review, we synthesize recent progress in the temporal ordering and spatial patterning of SCC evolution and discuss how genetic alterations, epigenetic remodeling, and tissue ecology jointly drive disease progression. We further highlight the implications for early interception, biomarker development, immune evasion, and evolution-informed prevention and therapy.