Cytokeratin expression in squamous cell carcinoma of the lung and oral cavity - An immunohistochemical study with possible clinical relevance

Objective. Serologic identification of the fragment of cytokeratin 19 known as CYFRA 21-1 has been used for Early detection of squamous cell carcinoma of the lung. The sensitivity of the CYFRA 21-1 assay in detecting oral cancers is lower than that in detecting lung cancers. To clarify the reason for this, we compared the cytokeratin expression in these cancers, with special reference to cytokeratin 19. Study design. Oral squamous cell carcinomas and lung squamous cell carcinomas were immunostained with cytokeratin 19, cytokeratin 10, and cytokeratin 13 antibodies. Staining intensity was scored on a graduated scale from 0 to 4. Results. With respect to cytokeratin 19, the stainings of all lung cancers were scored as 4, which indicates a greater Expression of cytokeratin 19 than is seen in oral cancers (p < 0.01). With an average cytokeratin 19 staining score of 1.67, oral cancers ranked lowest among the antibodies. Squamous cell carcinomas of the maxillary sinus arising from pseudostratified ciliated epithelium were highly expressive of cytokeratin 19. A marker for keratinizing cells (cytokeratin 10) and a marker for squamous cells (cytokeratin 13) were expressed more frequently and intensely in oral cancers (p < 0.01) than in lung cancers (p = 0.019). Conclusions. From the viewpoint of immunohistochemistry, cytokeratin 19 was found to be a tumor marker with low specificity and sensitivity in oral cancers. The staining results suggested that poor expression of cytokeratin 19 by oral squamous cell carcinoma may result in a low serum value of CYFRA 21-1 in patients with this condition.