Evaluation of nucleolar organizer regions in tumours of the jaw bones.

Nucleolar organizer regions [NORS] are loops of DNA that transcribe to ribosomal RNA. They can be visualized as intranuclear black dots by histochemical staining with a colloid silver solution. Silver stained nucleolar proteins (AgNORs) were counted in a variety of jaw bone tumours. In osteosarcomas, the number of AgNORs was also quantified before and after chemotherapy. Malignant bone tumour cells possessed more than five small AgNORs (5.54 +/- 0.44). Nuclei of benign jaw bone tumour cells had less than three (2. 97 +/-0.61). A significant difference in the number of AgNORs between osteosarcoma before chemotherapy (5.76 +/- 0.50) and after chemotherapy (3.89 +/- 1.65) was observed. (P < 0.05). The number ofAgNORs in recurrent osteosarcoma, recurrent ameloblastic carcinoma and recurrent chondrosarcoma was much higher than in their respective primary lesion but without statistical significant difference. The results of the present study indicate that the AGNOR count might help in determining malignancy, evaluating the effect of chemotherapy, and deciding the prognosis.