Decreased cytokeratin 13 expression in oral submucous fibrosis.

Oral submucous fibrosis (OSF) is a precancerous condition. This point of view is supported by a high frequency of oral epithelial dysplasia, oral leukoplakia, and oral squamous cell carcinoma (OSCC) found in patients with OSF. In this study, we used an immunohistochemical technique to study the expression of cytokeratin 13 (CK13) in 16 specimens of normal buccal epithelium, 8 specimens of the epithelium covering an oral fibroma, 16 specimens of oral epithelial hyperplasia, 13 specimens of oral epithelial dysplasia, 25 specimens of the epithelium adjacent to an OSCC, 47 specimens of OSF epithelium, and 28 specimens of OSCC. We found 3 distinct patterns of CK13 expression in these specimens. The first group of specimens including the normal buccal epithelium, epithelium covering an oral fibroma, oral hyperplastic epithelium, and mildly dysplastic oral epithelium uniformly showed grade 5 (positive cells > 80% of all epithelial cells) CK13 expression. The second group of specimens including OSF epithelium and the epithelium adjacent to an OSCC demonstrated a great variation in CK13 expression with approximately 1/3 of specimens showing grade 5 CK13 expression and 2/3 showing marked attenuation of CK13 expression. The third group of specimens including moderately and severely dysplastic oral epithelium and malignant epithelium of an OSCC also exhibited a great variation in CK13 expression with more than 95% showing a marked decrease in CK13 expression. Because mild to severe dysplasia is frequently found in the epithelium adjacent to an OSCC and the CK13 expression pattern in OSF epithelium is similar to that in dysplastic oral epithelium and to that in the epithelium adjacent to an OSCC, we suggest that OSF may be a premalignant lesion. [ABSTRACT FROM AUTHOR]