Hydropic degeneration refers to which histologic change?

• A. Intracellular edema restricted to keratinocytes of the stratum basale.
• B. Extracellular edema in the dermis.
• C. Necrosis of keratinocytes.
• D. Hyperkeratosis of the epithelium

Answer: (A)

Hydropic degeneration is intracellular edema—cells swell as water floods in when their membranes or pumps fail due to injury. In the skin, this manifests as swelling of keratinocytes with pale, clear cytoplasm, typically described as ballooning degeneration in the epidermis. The key idea is that the change is inside the cell, not in the surrounding tissue space.

So the best description is intracellular edema of keratinocytes in the epidermis, often noted in the basal layer. Extracellular edema in the dermis would be fluid between cells, not within the cells themselves. Necrosis involves cell death with membrane rupture and nuclear changes, not just swelling. Hyperkeratosis is thickening of the outer layer, not cell swelling.