Nucleolar organizer regions in jaw tumours of cartilaginous origin

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 cases comprising of primary chondrosarcomas of three histologic grades, in chondromyxoid fibroma and in controls comprising of normal bone and cartilage tissues of the jaw bones. The AgNOR counts increased step-wisely from normal bone tissue [1.11 0.4], chondromyxoid fibroma [2.66 0.78], grade I chondrosarcoma [3.94 0.34], grade II chondrosarcoma [4.32 0.52], and grade III chondrosarcoma [5.54 0.44]. There was a statistically significant difference in the mean AgNOR counts between grade 1 and grade III chondrosarcoma [p < 0.05]. The mean AgNOR counts for benign cartilaginous [chondromyxoid fibroma] tumour was significantly lower than the mean, AgNOR count for malignant cartilaginous tumours [chondrosarcomas] [p < 0.05]. The results in the present study indicate that silver colloid staining is a useful technique for evaluating the proliferative activity of chondrosarcoma and benign cartilaginous tumour such as chondromyxoid fibroma.