Necrosis
Messy, uncontrolled cell death, where the cell bursts and spills its contents. In tumours it usually means cells have outgrown their blood supply and starved.
Unlike apoptosis, necrosis releases the cell's contents into the surroundings, provoking inflammation; a necrotic core is common in fast-growing tumours whose centres lie too far from a blood vessel to get oxygen, and pathologists note its presence as a marker of aggressiveness in tumours such as glioblastoma. Necrosis after treatment (on imaging or in a surgical specimen) can be a sign that a drug or radiation has worked, and 'pathologic complete response' means no living tumour cells remain. Necroptosis and pyroptosis are regulated forms of necrosis that the cell can be induced to undergo and that, because they are inflammatory, may help alert the immune system.