Iron Stain (Prussian Blue)

The iron stain, also called Prussian blue or Perls' stain, turns iron in tissue bright blue. Because asbestos bodies are coated with an iron-rich protein, the stain makes them easy to see and count in lung tissue. It is a standard tool for confirming asbestosis and documenting asbestos exposure under the microscope.

Origin

The German pathologist Max Perls described the reaction in 1867, using a chemical that forms the pigment Prussian blue when it meets iron. Pathologists studying asbestos lung disease adopted it because the coating on asbestos bodies stains strongly.

Significance in Asbestos Context

When the body tries to clear an asbestos fiber, cells coat it with iron and protein, forming a beaded rod called an asbestos body or ferruginous body. On ordinary H&E slides these can be hard to spot; on an iron stain they stand out. Pathologists use iron-stained sections to count asbestos bodies, and the CAP-Roggli criteria for diagnosing asbestosis in tissue call for interstitial fibrosis together with a minimum number of asbestos bodies per square centimeter of lung. The stain has limits: most fibers in the lung, especially chrysotile, never become coated, so a low count does not prove low exposure. A fiber burden analysis, which dissolves tissue and counts fibers by electron microscopy, gives a fuller picture. Iron stain results are often central to proving asbestosis in a lung cancer claim based on tissue.

Example Sentence

The iron stain showed four asbestos bodies per square centimeter in areas of interstitial fibrosis, meeting the pathologic criteria for asbestosis.

Related Terms

Asbestos Bodies, Ferruginous Bodies, CAP-Roggli Histologic Criterion, Asbestosis, Fiber Burden Analysis, Tissue Digestion, Hematoxylin and Eosin (H&E) Stain

Notes

• If lung tissue was removed, ask whether iron stains were done to look for asbestos bodies.
• A report of "no asbestos bodies seen" on a small sample does not rule out exposure; ask your lawyer about further analysis.
• Ask that remaining tissue blocks be preserved for possible fiber burden testing.