Which nuclear feature is characterized by condensation of the chromatin into a small, dense mass?

• A. Pyknosis
• B. Karyorrhexis
• C. Karyolysis
• D. Hyperchromasia

Answer: (A)

The main idea here is that certain nuclear changes reflect how a cell is responding to injury. Condensation of the chromatin into a small, dense mass describes pyknosis. In pyknosis, the nucleus shrinks and becomes intensely basophilic because the chromatin clumps together. This is an early sign of irreversible cell injury and is often seen before the nucleus fragments or dissolves. If the injury progresses, the pycknotic nucleus can undergo fragmentation (karyorrhexis) and then dissolution (karyolysis). Hyperchromasia, by contrast, means increased staining intensity due to more DNA but does not specifically describe a small dense nuclear mass.