• Intratumoral microbiota are diverse microbial communities residing within tumors, distinct from classical oncogenic pathogens, and they modulate tumor progression, immune evasion, and therapeutic response.
• Origins of intratumoral microbiota include translocation from mucosal reservoirs, direct invasion from adjacent normal tissues, and hematogenous dissemination from distant sites.
• Pan-cancer analyses reveal distinct microbial profiles across tumor types, with bacteria predominating over fungi, and these profiles correlate with tumor heterogeneity.
• Targeting intratumoral microbiota presents a promising therapeutic avenue, but challenges remain in understanding colonization mechanisms and clinical translation.