Immunoexpression of cytokeratin-19 in the oral lichen planus and related oral squamous cell carcinoma

Aims: Cytokeratin 19 (CK-19) is an epithelium-specific intermediate filament protein that has been investigated in oral lichen planus (OLP) lesions but has not been compared with the expression of CK-19 in the OLP-related oral squamous cell carcinoma (OSCC). The aim of the present study has been to objectively compare the immunohistochemical expression of the CK-19 in OLP lesions and subsequent OSCC lesions that developed over time, to evaluate the change of the staining pattern among OLP and the grades of differentiation in OSCC. Methods: Thirty-six formalin-fixed tissues of 18 OLP patients (18 samples from OLP lesion and 18 samples from OLP-related OSCC lesion) were included. The monoclonal antibody for CK-19 was used at 1:100 dilution for the immuno-staining on 4-μm thick sections. Staining pattern of CK-19 was graded into a 4-point scale: (1) no staining, (2) only few cells staining, (3) less than 50% of the cells stained, and (4) 50% or more of the cells stained. Microslides were examined under the light microscope using objective lenses magnifications of 4×, 10×, and 20×. Results: The CK19 positive rate in OLP tissues was 33% (6 out of 18) and 56% (10 out of 18) in OSCC tissues. The CK19 positive score in OSCC tissues was significantly higher than that in the corresponding OLP tissues (Mann-Whitney test, P=0.02). Well-differentiated OSCC showed significantly lower of C-K19 scores than those moderately differentiated grades (Mann-Whitney, P=0.007). Conclusions: The quantity and distribution of CK-19 staining in OSCCs showed relevant difference in comparison with OLP lesions. The increased of CK19 protein expression in OSCC tissues correlates significantly with the pathologic differentiation grade.