Immunogold labelling of PCNA and Ki-67 antigen at the ultrastructural level in laryngeal squamous cell carcinoma and its correlation with lymph node metastasis and histological grade

Streptavidin-gold was used for the immunolocalization of PCNA and Ki-67 antigen at the ultrastructural level with a postembedding technique in biopsies of 15 patients with laryngeal squamous cell carcinoma. Positive immunoelectron staining was obtained in 9 cases for PCNA (60%) and in 8 cases for Ki-67 (53%). PCNA was predominantly found in heterochromatin of the nucleus of laryngeal carcinoma cells in a granular pattern. Positivity for PCNA was not found in nucleoli. In 4 cases, positive staining was observed both in nucleus and cytoplasm. In the cytoplasm, it was found to be present on the endoplasmic reticulum and on ribosomes throughout the cytoplasm. Ki-67 antigen was localized in the nucleus where it was associated with heterochromatin and euchromatin. It was also observed in nucleoli in all cases. Cytoplasmic localization of Ki-67 antigen was similar to that of PCNA. All 8 cases that were positive for Ki-67 were also positive for PCNA. Control incubations did not result in labelling with steptavidin-gold particles for both antigens. A significant correlation between PCNA and Ki-67 expression in association with pathological characteristics such as nodal status and histological grade was not found. Our data indicate that Ki-67 antigen staining correlates with PCNA labelling, whereas a relationship between proliferation markers and tumour progression was not found.