Nucleolar organizer regions in soft tissue sarcomas

Argyrophilic proteins of nucleolar organizer regions (AgNORs) were studied in a series of 65 sarcomas of the soft tissues and 2 cases of fibrohistiocytic tumors of intermediate malignancy. The numbers of AgNORs per nucleus and the size of AgNORs were determined and compared with pathomorphologic parameters such as grading of malignancy, cellularity and tumor diameter. The main finding of this study was that AgNOR counts showed significant differences between low-grade malignant (G 1) and high-grade malignant (G 3) tumors predominantly based on a correlation with the frequency of mitosis. All the other criteria of tumor grading (nuclear pleomorphism, differentiation, amount of necrosis), tumor diameter and cellularity showed no differences with regard to AgNOR counts. Though it was observed that tumor giant cells possessed predominantly coarse granular AgNORs, no correlation was found between AgNOR size and any of the parameters investigated. In spite of a clear statistically significant result gained by an evaluation of all cases, a heterogeneity of AgNORs in relation to mitotic activity within a few histological tumor types could be observed, making it difficult to suggest the determination of AgNORs as a parameter with general validity for all soft tissue sarcomas.