A carcinogenic agent works by damaging the DNA of a cell or disrupting metabolic processes, leading to uncontrolled cell division and the formation of malignant tumors. These agents are classified by organizations like the International Agency for Research on Cancer (IARC) into groups based on the strength of evidence for their cancer-causing potential. While some carcinogens act directly on DNA (genotoxic), others promote cancer through chronic inflammation or immunosuppression.