Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
When chemotherapy leaks out of the vein into the tissue around it, some drugs can kill that tissue and leave a serious wound.
The Leaking Pipe in the Wall
Imagine a water pipe running through your house wall that delivers hot water safely to your radiators — the pipe is like the vein, and the hot water is like the chemotherapy. As long as the water stays inside the pipe, it travels where it's supposed to go and does its job. But if the pipe cracks or the joint loosens, hot water floods into the wall cavity (the tissue space) instead. The water immediately starts cooking the drywall and insulation it touches — just like chemo kills any cell it contacts. The wet, damaged wall swells up and presses back on the pipe so hard the water stops flowing, which is your signal that something is very wrong. By then, the wall is already ruined, and you need to cut it out and replace it with new material.
Oncology Nursing Society (ONS) Chemotherapy and Immunotherapy Guidelines · American Society of Clinical Oncology (ASCO) · National Comprehensive Cancer Network (NCCN) · European Oncology Nursing Society (EONS) Extravasation Guidelines · reviewed 2026-07-07