Histopathological and Ultrastructural Evaluation of Buccinator Muscle Alterations in Oral Submucous Fibrosis: A Descriptive Light and Transmission Electron Microscopic Study.

INTRODUCTION: Oral submucous fibrosis (OSMF) is a chronic, progressive, potentially malignant disorder characterized by fibrosis of the oral mucosa and progressive restriction of mouth opening. The present study aimed to descriptively evaluate the histopathological and ultrastructural alterations of the buccinator muscle in patients with OSMF using light microscopy and transmission electron microscopy (TEM). MATERIALS AND METHODS: This descriptive observational study included 10 buccal mucosal biopsy specimens from 7 patients clinically diagnosed with OSMF and 3 healthy controls. Consecutive sampling was employed, and biopsy specimens measuring approximately 5 × 5 mm, including the underlying buccinator muscle, were collected. One portion of each specimen was processed for hematoxylin and eosin (H&E) staining and examined under a light microscope, whereas the remaining tissue was processed for transmission electron microscopy. Histopathological features, including muscle fiber atrophy, splitting, hyaline degeneration, fibrosis, vascular alterations, and ultrastructural changes involving myofibrils, myofilaments, mitochondria, muscle nuclei, autophagic vacuoles, and collagen deposition, were descriptively documented. RESULTS: Among the 7 OSMF cases, 2 (28.6%) were clinically classified as grade I, 4 (57.1%) as grade II, and 1 (14.3%) as grade III based on mouth opening. Light microscopic examination revealed muscle fiber atrophy, splitting of muscle fibers, flocculent degeneration, hyaline degeneration, and fibrosis in all OSMF specimens. Constricted blood vessels were observed in 5 (71.4%) specimens, and vacuolar degeneration and dilated blood vessels were identified in 2 (28.6%) specimens each. Transmission electron microscopy revealed loss of myofibrils, loss of myofilaments, focal disruption of I bands and Z lines, irregular Z lines, enlarged mitochondria, enlarged muscle nuclei, autophagic vacuoles, and collagen replacement of muscle fibers in all OSMF specimens. No alterations were observed in the control specimens. CONCLUSION: This exploratory descriptive study demonstrated consistent histopathological and ultrastructural degeneration of the buccinator muscle in OSMF. Although the findings provide preliminary evidence of skeletal muscle involvement, they should be interpreted cautiously because of the small sample size, and larger studies are needed to validate these observations.