Oncosis

Oncosis is a term used in pathology to describe a form of cell injury characterized by cellular swelling and the subsequent onset of necrotic death. The word derives from Greek onkos, swelling. Oncosis denotes the early hydropic change that occurs when a cell experiences energy failure.

The mechanism typically involves energy depletion from ischemia, hypoxia, toxins, or other stresses that impair ATP production. Loss of ATP disrupts ion pumps such as Na+/K+-ATPase, leading to an influx of sodium and water into the cytoplasm. The cell swells, a process called hydropic change, and organelles swell as well, with plasma membrane blebbing and dilation of the endoplasmic reticulum and mitochondria. If the injurious stimulus persists, membrane integrity deteriorates, lysosomes may rupture, and intracellular components are degraded. Nuclear changes associated with necrosis, including karyolysis, may occur subsequently.

In contrast to apoptosis, oncosis-related cell death is typically associated with rapid loss of membrane integrity and an inflammatory response due to the release of intracellular contents. Clinically and pathologically, oncosis is observed in tissues subjected to ischemia, toxins, or severe physical injury and often marks the necrotic process.

Terminology varies: some authors reserve oncosis for the swelling phase of necrosis, while others use it more broadly to refer to necrotic cell death itself. In contemporary literature, the term necrosis is frequently used, with oncosis noted as a historical or descriptive descriptor of the swelling changes underlying necrosis.