Prognostic Significance of Nuclear Accumulation of c-myc and mdm2 Proteins in Synovial Sarcoma of the Extremities

We retrospectively analysed a group of primary tumours from 32 patients with synovial sarcomas of the extremities by using immunohistochemistry on paraffin-embedded tissue samples in order to investigate the prognostic significance of the nuclear accumulation of c-myc and mdm2 proteins. Nuclear positive immunostaining for c-myc or mdm2 proteins were revealed in 9/32 cases (28%) and in 6/30 cases (20%), respectively. Since c-myc protein appears to be a key factor for keeping cells in an active proliferative stage, we also analysed the growth compartment of each tumour by using the MIB1 monoclonal antibody, specific for Ki-67 antigen. A high MIB1 index was found in 8/31 cases (26%) but was not associated either with c-myc or mdm2 nuclear positivity. Analysis of clinical outcome was performed in a subgroup of 27 patients with a minimum follow-up of 24 months. Among the clinicopathologic parameters and the biological markers, only the nuclear accumulation of c-myc was significantly associated with a higher relapse rate (p = 0.03). Accordingly, survival analysis confirmed a trend toward a poor event-free survival rate and a worse outcome in c-myc-positive cases (p = 0.12). These data demonstrate that assessment of c-myc nuclear accumulation can be useful to identify high-risk subsets of patients with synovial sarcoma of the extremities.