Nucleolar organizer regions in parosteal and central osteosarcomas

Silver stained nucleolar organizer regions (AgNOR) have revealed differences in the biological behavior of certain entities. This study involves a morphometric analysis of AgNOR in 6 central, classic osteosarcomas and 6 parosteal osteosarcomas. There was a statistically significant difference in the number of AgNOR per nucleus between central and parosteal osteosarcomas. Single AgNOR volume was smaller in central osteosarcomas as compared to parosteal osteosarcomas. However, this difference did not reach statistical significance. The parameter AgNOR number per nucleus revealed a cut off value such that 100% of central osteosarcoma cases lay above this value and 100% of parosteal osteosarcoma cases lay below this value. AgNOR demonstration involves a simple technique which can be performed on formalin fixed, paraffin embedded file material. Thus, it may be prudent to routinely assess AgNOR as a contributor to the determination of the pathophysiology of osteosarcomas.