The late nineteenth and early twentieth centuries solidified radical oncologic resections as the central strategy in cancer surgery, with en bloc removal and standardized margins guiding breast, colorectal, head-and-neck, and abdominal procedures. Across specialties, investigators and surgeons integrated pathology, anatomy, and the early study of cancer genetics to inform broad operations and staged dissections, signaling a shift toward organ-level restoration and outcome-focused practice. This convergence across disciplines reveals a unified push toward systematic tumor management and the emergence of surgical oncology as a distinct clinical paradigm. Historical Significance: The period reframed cancer as a disease addressed by aggressive, field-defining operations, establishing foundational principles of oncologic resection that endured for decades. The introduction of genetic and systemic considerations began to shift the view of tumors from purely local processes to complex, heritable entities with systemic implications. By codifying margins, en bloc dissection, and site-specific protocols, this era laid the groundwork for future advances in oncologic planning, reconstructive strategies, and the integration of pathology, physiology, and genetics into surgical decision-making.