Traditional tumor biology has predominantly focused on the pathological characteristics and evolution of localized lesions. However, with the deepening of research, solid tumors should be redefined as a systemic disease entity that originates locally but exerts systemic influence.This paper systematically elaborates the core connotation of this concept: the occurrence and development of a tumor is a dynamic process involving the remodeling of systemic signaling networks. From the precancerous lesion stage, biomarkers released by dysplastic cells can be detected in the circulation.Neoplastic tissues continuously disseminate individual cancer cells, most of which are effectively cleared by the immune system; only when cell microspheres (e.g., circulating tumor cell clusters) with stronger survival and metastatic potential successfully escape and colonize, can distant metastasis occur. Based on this, the essence of cancer therapy should be the synergistic initiation of local lesion eradication and systemic anti-cancer mechanisms, especially immune surveillance.For advanced cancers, it is necessary to integrate local resection, chemotherapy, targeted therapy, and the rebuilding and enhancement of systemic anti-cancer immunity to form a multimodal combination therapy strategy.This systemic concept provides a new theoretical framework for cancer prevention, early diagnosis, treatment, and prognosis evaluation.