STANDARDIZED DEMONSTRATION OF SILVER-STAINED NUCLEOLAR ORGANIZER REGIONS-ASSOCIATED PROTEINS IN ARCHIVAL ORAL SQUAMOUS-CELL CARCINOMAS AND ADJACENT NONNEOPLASTIC MUCOSA

Standardized silver staining and quantitation of nucleolar organizer r egions-associated proteins (AgNORs) on routinely formalin-fixed and pa raffin-embedded tissues has been recently established. The present stu dy was designed to assess its applicability and reproducibility on arc hival oral squamous cell carcinoma specimens, with special emphasis on the invasive tumor front, Standardized image cytometric AgNOR analysi s was performed at the invasive zone and central parts of the tumors a s well as in adjacent dysplastic and normal oral mucosa by applying a modified silver staining on routinely processed archival tissues after wet autoclave pretreatment for protein retrieval. A statistically hig hly significant and reproducible difference of all of the four standar dized AgNOR parameters evaluated (mean AgNOR number, mean AgNOR area, coefficient of variation (CV) of AgNOR number, and CV of AgNOR area pe r nucleus) was observed between the different areas assessed; there wa s a statistically significant gradual decrease in the CV of the AgNOR number from the invasive tumor front to central parts of the carcinoma s, from dysplastic mucosa to normal epithelium. The observed increase of AgNORs at the invasive front of oral squamous cell carcinomas seems to indicate a subgroup of tumor cells with increased biosynthetic act ivity and malignant potential. Wet autoclave pretreatment before silve r staining of AgNORs is necessary for a reliable visualization of sing le AgNOR dots. Second-order statistics of AgNOR features, e.g., CV val ues, offer a potent and highly reproducible parameter for AgNOR quanti tation.