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Microscopic Features of Necrosis

necrosis

For medical students2 min readUpdated 2026-10-10

The microscopic picture of necrosis reflects profound, irreversible damage to cells and the extracellular matrix driven by activated hydrolases. These changes affect all cellular structures—from organelles and the nucleus to the cytoplasm and stroma.

Early diagnosticsRequires specialized methods: polarization and fluorescence microscopy, histochemistry, and electron microscopy.
Nuclear stagesKaryopyknosis, karyorrhexis, and karyolysis sequentially reflect cell death.
CytoplasmUndergoes coagulation, plasmorrhexis, and plasmolysis with increased eosinophilia.
Stromal enzymesNeutral proteases and lipases destroy matrix fibers and lipid components.

Ultrastructural Organelle Changes

At the subcellular level, tissue death is evident early on. Chromatin margination and aggregation are observed in the nucleus. Mitochondria swell, their matrix loses density, and irregular calcium salt deposits form within them. The endoplasmic reticulum exhibits swelling and membrane fragmentation, a reduced ribosome count, and detachment of polysomes. Lysosomes undergo membrane rupture with clearing of the matrix. Glycogen granules completely disappear from the cytoplasmic matrix, enzymatic activity drops, and myofibrils fragment.

Nuclear and Cytoplasmic Changes in Light Microscopy

Light microscopy reveals changes associated with the activation of ribonucleases and deoxyribonucleases.

Stages of Nuclear Death:

  1. Karyopyknosis — marked nuclear shrinkage.
  2. Karyorrhexis — fragmentation of nuclear structures into discrete clumps.
  3. Karyolysis — complete dissolution of the nucleus.

Stages of Cytoplasmic Changes:

Due to protein denaturation and the loss of basophilic RNA, the cytoplasm acquires a bright pink color upon hematoxylin and eosin staining (increased eosinophilia). The cell becomes glassy and takes on a "moth-eaten" appearance due to organelle destruction and glycogen washout.

Lipid Alterations and Stromal Damage

In dead cells, damaged membranes form myelin figures—large whorls of phospholipid masses that can be phagocytosed or broken down into fatty acids. The accumulation of fatty acids shifts the pH toward the acidic range, forming calcium soaps and leading to calcification.

Necrosis also affects the extracellular matrix and fibrous stromal structures through enzymatic action:

Mnemonic

The sequence of nuclear changes is easily remembered by the acronym PKL: Pyknosis (shrinkage) → Karyorrhexis (fragmentation) → Lysis (dissolution).

Frequently asked questions

What histochemical reactions and markers are used for the early diagnosis of necrosis?

Specialized microscopy and histochemical techniques are used for early diagnosis.

  • Fluorescence microscopy — performed using acridine orange.
  • Histochemistry (PAS reaction) — detects a decrease or disappearance of glycogen granules from the cytoplasm (e.g., in cardiomyocyte sarcoplasm).
  • Polarization microscopy — allows detection of myofibrillar relaxation.

Additionally, electron microscopy is used to identify ultrastructural signs of organelle damage.

How does the microscopic picture of coagulative necrosis differ from liquefactive necrosis?

The microscopic picture of these necrosis types differs in the state of the cytoplasm and nuclei.

FeatureCoagulative NecrosisLiquefactive Necrosis
CytoplasmCompaction and coagulation of protein structuresLiquefaction (colliquation) of the cytoplasm
NucleiHyperchromasia and pyknotic changes appear immediatelyKaryolysis, karyorrhexis, and nuclear/cytoplasmic fragmentation join later
Tissue StructureTubular outlines are preserved in infarct coagulative necrosisDisintegration of nuclei and cytoplasm occurs
What are the tissue-level outcomes of necrosis?

At the tissue level, several favorable outcomes of necrosis are distinguished, associated with demarcation and repair processes.

  • Organization — replacement of necrotic masses by connective tissue (scarring).
  • Encapsulation — demarcation of the necrotic area by a connective tissue capsule.
  • Petrification — dystrophic calcification, the deposition of calcium salts in necrotic masses.
  • Ossification — a rare outcome characterized by bone tissue formation within the necrotic zone.
  • Cyst — a cavity formed at the site of a large softening focus in liquefactive necrosis.
  • Mesoglial scar — forms with small foci of liquefactive necrosis in the brain.
Why does the cytoplasm become bright pink during necrosis on H&E staining?

Increased eosinophilia occurs due to eosin binding to denatured cytoplasmic proteins and the loss of basophilia associated with the depletion of ribosomal RNA.

What are the main stages a cell nucleus undergoes during necrosis?

There are three sequential stages: karyopyknosis (shrinkage), karyorrhexis (fragmentation into clumps), and karyolysis (complete dissolution).

What are myelin figures and how do they form?

These are large whorls of phospholipid masses formed from damaged cell membranes as a result of lipoprotein dissociation and subsequent water intercalation.

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