Significance of proliferating cell nuclear antigen and argyrophilic nucleolar organizer regions in bone and soft-tissue spindle-cell tumors - PCNA-AgNORs index as a new parameter

Background. The grading of musculoskeletal spindle-cell tumors presents considerable problems. It is obvious that the prediction of the biological behavior in an individual may not always be possible when the conventional histological criteria (such as H and E/staining) are used. Methods. We investigated the expression of proliferating cell nuclear antigen (PCNA) and the number of argyrophilic nucleolar organizer regions (AgNORs) in paraffin sections of bone and soft tissue spindle-cell tumors from 41 patients. Results. The percentage of PCNA-positive cells per 600 nuclei was 35.4% in benign tumors (I); 38.8% in intermediate tumors (II); and 51.7% in malignant tumors (III) (II versus III, P < 0.05). (Tumors were graded as I, II, or III by histologic finding from H and E staining and according to clinical follow- up.) The average AgNORs score was 1.4 dots in (I); 1.9 dots in (II); and 3.0 dots in (III). There was a significant correlation between the AgNORs score and the histological grade (I versus II, P < 0.01: II versus III, P < 0.05: I versus III, P < 0.01). As a new parameter, a PCNA-AgNORs index plotted for individual patients afforded a cutoff value (1.0 dots · % /100) that proved to be useful for identifying histological grade, particularly for the differential diagnosis of intermediate and malignant tumors (I or II versus III, P < 0.001; I versus II, P < 0.05). Conclusion. The PCNA-AgNORs index is a good new parameter for assessing the histological grade of musculoskeletal spindle-cell tumors for the clinician and could be used as a routine examination.