IMMUNOLOCALIZATION OF THE RETINOBLASTOMA AND MYC PROTEINS IN HUMAN HEAD AND NECK-CANCER

Myc gene amplification and enhanced expression, and loss of expression of the retinoblastoma (Rb) gene product have been demonstrated in man y common malignancies and correlated with disease behavior. To our kno wledge, Rb immunoreactivity has yet to be reported in head and neck ca rcinomas. We evaluated Myc and Rb protein immunolocalization in head a nd neck carcinomas to determine whether Myc immunostaining is enhanced and Rb staining is lost in this malignancy. Immunohistochemical stain ing was used to evaluate seven primary and matched metastatic head and neck carcinomas. Cytoplasmic Myc staining was enhanced in tumor tissu e relative to normal adjacent tissue in nine of 14 specimens, consiste nt with previous reports demonstrating gene amplification and overexpr ession of Myc in head and neck tumors. Rb immunostaining was documente d with no difference noted between the primary and metastatic tumor ti ssue studied. Within tumor tissue from a given patient, areas of moder ate to poorly differentiated carcinoma showed reduced Rb nuclear stain ing compared to adjacent foci of well differentiated malignant cells. In two patients (four specimens), there was a total absence of nuclear Rb staining. The lack of nuclear Rb staining in the primary tumor and metastasis from these two patients suggests the loss of functional Rb in these four specimens, and the need for larger studies to determine if loss of Rb staining occasionally correlates with the development o f this malignancy.