Elastic Fiber Staining of Slide Sections: A Technique to Observe Gastric Cancer Metastasis

Elastic fiber staining helps examine cancer cell invasion beyond the peritoneal elastic lamina or the sub-mesothelial elastic tissue.

To begin, add potassium permanganate solution to a processed tissue section, followed by immersion in oxalic acid. The strong oxidizing property of the potassium permanganate-oxalic acid combination bleaches the natural pigment from the tissue section to prevent interference with the staining process by obscuring elastic fiber morphology.

Rinse the slide with water and ethanol to remove any residual bleaching agent. Next, incubate the specimen in an elastin stain that comprises an iron-hematoxylin complex. Elastin, the main elastic fiber component, has a strong affinity for iron-hematoxylin complexes. 

Wash the slide with ethanol and water to remove any residual stain. Finally, treat the specimen with a counterstain containing picric acid and Ponceau S. The smaller picric acid molecules penetrate all tissue types but are firmly retained by the close textured muscle and cancer cells. In contrast, the larger Ponceau S molecules displace picric acid in the porous-textured collagen, causing collagen to be stained differently from the muscle and cancer cells.

When observed under a microscope, elastic fibers appear as blue-black filaments. Collagen stains red, while muscle and cancer cells appear yellow. Yellow cancer cells penetrating the blue-black elastic lamina confirm metastatic invasion.