Prognostic significance of mast cells in soft tissue sarcoma.

We counted the number of toluidine blue positive mast cells within and around the tumor in 44 patients with soft tissue sarcomas (STS). Irrespective of their histologic types, these cases were broadly divided into the following two groups: (1) low count (less than 20 mast cells/10 high-power fields [HPF]) and (2) high count (greater than or equal to 20 mast cells/10 HPF). The patients with a high mast cell count showed a significantly better 5-year survival rate than those with a low count (85.9% versus 30.5%; P less than 0.01). Five patients with distant metastases at first admission all belonged to the low count group. These results suggest that the number of mast cells within and around the tumor is a useful prognostic factor for STS.