Immunohistochemical study of epidermal growth factor receptor in adenoid cystic carcinoma of salivary gland origin

Background. Epidermal growth factor (EGF) and its receptor (EGFR) are involved in the development of salivary gland tumors. Recently, treatment modalities for EGFR inhibition have shown an enhanced clinical response in carcinomas of different locations. Adenoid cystic carcinoma (ACC) of salivary gland origin is a malignant tumor with a poor long-term outcome. If salivary gland ACC does exhibit EGFR, then immunotherapy could have a major impact on improving its prognosis. Methods. The study consisted of 34 samples of formalin-fixed, paraffin-embedded specimens of salivary gland ACC. Specimens were stained with a mouse antihuman monoclonal antibody for immunohistochemical detection of EGFR. Overlying oral mucosa and adjacent normal salivary ducts served as internal controls. Both membrane and cytoplasmic staining were evaluated. Staining score was calculated by multiplying the percentage of positively stained tumor cells by the intensity of the staining. The highest score for a given tumor was equal to 2. Results. In the final analysis, 27 of the 34 specimens were included; 7 were excluded, because the internal control did not reveal any staining. Of these 27 specimens, 23 (85%) stained positively for EGFR with a staining score of 0.05 to 1.8. Three palatal tumors attained the highest scores (one tumor, 1.2, and the remaining two, 1.8). Conclusions. Most salivary gland ACC stained positively for EGFR, and in some the staining was quite intense. On the basis of the already proven antitumoral effect of agents acting as EGFR inhibitors, it is suggested that patients with ACC might benefit from these agents, especially when surgery has failed or in those with recurrent or metastatic disease.