Somatic tissues maintain homeostasis through regulatory mechanisms that constrain proliferation — contact inhibition, which halts division when neighboring cells are detected, and apoptosis, a cell-intrinsic self-destruction program triggered when a cell recognizes its own damage. Because the body generates cells in enormous daily volume, replication errors are statistically inevitable; most are inconsequential or resolved by apoptosis, but a mutation that simultaneously disables apoptosis and accelerates division produces a clonal population of defective cells termed a neoplasm or tumor, classified as benign when growth is bounded and non-invasive. Malignancy arises when further mutations confer uncontrolled growth, invasion of surrounding tissue, and metastasis (dissemination to distant sites), a progression driven by mutations that damage the DNA replication machinery itself and thereby raise the mutation rate. The concept belongs to cell biology and oncology, framing cancer not as a single disease but as a class of outcomes of broken mitosis and DNA replication, which explains why treatment resistance evolves and why therapies target rapid proliferation as the shared trait.
Somatic tissues maintain homeostasis through regulatory mechanisms that constrain proliferation — contact inhibition, which halts division when neighboring cells are detected, and apoptosis, a cell-i…