Epidermal growth factor receptor immunoreactivity in human laryngeal squamous cell carcinoma

Epidermal growth factor receptor (EGFR) is a transmembrane protein receptor with tyrosine kinase activity. The protein has cysteine-rich sequence repeats in its extracellular ligand-binding domains. Elevated levels of EGFR are associated with malignant transformation of squamous cells and are observed in squamous cell carcinomas from the lung, head, neck, skin, cervix and esophagus. We examined the expression of EGFR in laryngeal squamous cell carcinoma (SCC) (N = 24) and non-neoplastic polyps (N = 7) using streptavidin-biotin immunohistochemistry and a monoclonal antibody (Serotec: MCA-571) to the EGFR protein. The carcinomas were classified as well differentiated (N = 2), moderately differentiated (N = 16) and poorly differentiated (N = 6). Tissues from metastatic tumor deposits in lymph nodes (N = 5) were also studied. Overexpression of EGFR was present, in the form of strong cytoplasmic immunostaining, in the majority of the SCC cases (n = 20; 83%) and in all of the metastatic tumor deposits. In contrast, although some of the vocal cord polyps showed weak (n = 2) to moderate (n = 5) immunoreactivity, none had evidence of strong EGFR immunoreactivity. The differences in EGFR immunoreactivity were significant between primary laryngeal SCC and vocal cord polyps (p = 0.0001; χ² test), and between metastatic laryngeal SCC and vocal cord polyps (p = 0.0001; χ² test). Laryngeal carcinoma cases which showed EGFR overexpression had a lower median survival period compared to those without overexpression. In conclusion, a different extent of EGFR expression is demonstrated in laryngeal squamous cell carcinomas and non-neoplastic vocal cord polyps using an immunohistochemical method. Some trends in the prognostic value of EGFR immunoreactivity in laryngeal carcinomas appear to emerge in this study.