Which of the following morphologic findings on light microscopy is considered the definitive evidence that cell injury has become irreversible?

• A Nuclear changes of pyknosis, karyorrhexis, or karyolysis ✓
• B Cellular swelling with clumping of nuclear chromatin
• C Detachment of ribosomes from the rough endoplasmic reticulum
• D Swelling and small amorphous densities within mitochondria

Explanation

Progression of nuclear changes (pyknosis, karyorrhexis, karyolysis) is the morphologic hallmark of irreversible injury and cell death on light microscopy; all other listed features can occur in reversible injury. Mitochondrial swelling, ribosomal detachment, membrane blebbing, and chromatin clumping are seen in early reversible ischemia. The single fact that kills distractor D is that amorphous matrix densities appear very early and do not by themselves signify irreversible damage.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.