Collagen fibers in oral submucous fibrosis - A polarizing microscopy study using two special stains

Oral submucous fibrosis (OSMF), a well-recognized oral potentially malignant disorder, results due to increased collagen production and reduced collagen degradation.

To qualitatively compare the staining properties of collagen in OSMF using two special stains based on their birefringent property using polarizing microscopy. The study also assessed the distribution and orientation of collagen fibers in different grades of OSMF.

A total of 73 subjects with different clinical and histopathological staging of OSMF comprised the study population. Histopathological examination was done using hematoxylin and eosin stain, Van Gieson and picrosirius red. Collagen fibers were analyzed for polarization colors, distribution, and orientation.

Picrosirius red stained both thick and thin collagen fibers. Irrespective of the histopathological grades reddish orange and yellowish orange were the most predominant colors. Parallel arrangement of fibers was observed when stained with Van Gieson but picrosirius red stained sections showed a majority of parallel type I fibers with perpendicular type III fibers which increased with advancement in the histopathological grade. Yellowish orange and greenish yellow fibers were predominant in the lamina propria, while reddish orange fibers were predominant in the submucosa.

Picrosirius red was found to be a better stain. Histopathological grading and polarization colors showed no association with each other. Collagen fibers were more thickly and tightly packed in the submucosa indicating that the process of fibrosis began there. The increase in perpendicular type III fibers with advancing histopathological grades suggested their role in fibrosis.