(covers information from several alternate timelines)
Necrosis (also known as tissue necrosis or cellular necrosis) was a form of cell injury which resulted in the premature death of cells in living tissue by autolysis.
In 2152, Doctor Phlox recorded there was extensive necrosis along the conductive pathway of the automated repair station's replica of Travis Mayweather's corpse's musculature. (ENT: "Dead Stop")
In 2258 of the [[alternate reality, Leonard McCoy injected Khan Noonien Singh's platelets into the deceased tissue of a necrotic tribble, in an attempt to figure out why Khan's cells regenerated so rapidly. Star Trek Into Darkness
In 2268, after Hikaru Sulu had been touched by Losira, Dr. Leonard McCoy discovered a layer of necrotic tissue a few cells thick in the helmsman's shoulder. (TOS: "That Which Survives")
Lesions displaying signs of necrosis indicated that a patient had entered the terminal stages of the Teplan blight. (DS9: "Inter Arma Enim Silent Leges")
In 2374, Chakotay began to suffer from tissue necrosis within a matter of hours as a result of illicit Srivani experiments. (VOY: "Scientific Method")
Borg nanoprobes could be used to reverse cellular necrosis. They were used to reanimate the deceased Neelix in 2374, although his tissues later began to necrotize when they rejected the nanoprobes, requiring careful monitoring of the condition. (VOY: "Mortal Coil", "Inside Man")
In 2376, a comatose B'Elanna Torres' lungs took in just enough oxygen to keep her brain from necrotizing. (VOY: "Barge of the Dead")
In 2378, omicron radiation from a Chokuzan weapon caused Icheb's cells to necrotize. (VOY: "Q2")
Gangrene was a type of necrosis.