Background: Gradual loss of cytokeratin 13 (CK13) may be linked with the severity of dysplastic changes and transformation to malignancy. In this study we assessed the differential expression of CK13 in normal, hyperplastic, dysplastic and cancerous oral mucosa.

Materials and Methods: A total of 93 oral biopsies were collected during the 2011-2014 period. The biopsies were characterized as normal (19), hyperplastic (21), severely dysplastic/carcinoma in situ (16) and invasive oral squamous cell carcinoma (OSCC) (37) after morphological assessment. Formalin fixed paraffin embedded sections were stained with a monoclonal antibody against CK13 using the Envision technique. Immunohistochemically stained slides were then analyzed for CK13 expression.

Results: CK13 was consistently and diffusely expressed in all normal and hyperplastic tissue biopsies from oral mucosa. Severely dysplastic/carcinoma in situ biopsies showed complete loss in 50% of cases, while in the remaining 50% expression was very focal and weak. OSCC cases showed complete or near complete loss of CK13 in all cases. Few cases showed weak expression in keratin pearls only.

Conclusions: This study validates the utility of CK13 IHC as a useful immunohistochemical marker in routine diagnostic practice to make distinction between non-neoplastic from dysplastic and neoplastic (malignant) oral lesions.