Deciphering the Molecular Landscape of Squamous Cell Carcinoma of the Anal Canal: From Biology to Precision Oncology.

Squamous cell carcinoma of the anal canal (SCAC) is a rare malignancy whose incidence has been steadily increasing worldwide. Persistent infection with high-risk human papillomavirus (HPV), particularly HPV16 and HPV18 genotypes, is the main etiological factor and plays a central role in tumor development. While combined chemoradiotherapy remains the standard treatment for localized disease and achieves high rates of tumor control, a considerable proportion of patients experience recurrence or present with advanced disease. For the latter, therapeutic options remain limited. Over the last decade, advances in genomic profiling have significantly expanded our understanding of SCAC biology. Recurrent alterations affecting the PI3K/AKT/mTOR pathway, especially PIK3CA mutations, have emerged as the most common molecular events, particularly in HPV-positive tumors. Additional alterations involve receptor tyrosine kinase signaling, chromatin remodeling genes, DNA damage response pathways, and components of the MAPK cascade. Moreover, HPV-positive and HPV-negative tumors display distinct molecular features with important prognostic implications. Immunotherapy has recently become an important component of treatment for advanced SCAC, although reliable predictive biomarkers are still lacking. This review summarizes the current evidence on the molecular landscape of SCAC, discusses emerging prognostic and predictive biomarkers, and highlights potential opportunities for the development of more personalized therapeutic strategies.