Upregulation of MMP9 expression in postradiation angiosarcoma of the breast: a possible predictive risk factor.

Postradiation angiosarcoma of the breast is a secondary angiosarcoma in breast carcinoma patients who have undergone radiation therapy. Although postradiation angiosarcoma is rare, it is very aggressive and has an extremely poor prognosis. Previous studies have implicated matrix metalloproteinase 9 (MMP9) in some cancer development and progression and angiogenesis. In this study, we compared MMP9 expression in surgical specimens from breast cancer patients treated with radiation who did and did not develop breast angiosarcoma within 15 years. We also compared MMP expression in the breast angiosarcoma specimens from patients with postradiation angiosarcoma of the breast and patients with non-breast angiosarcoma not previously treated with radiation. Our results showed that MMP9 was expressed in the endothelial cells in the breast carcinoma specimens from patients who developed angiosarcoma after radiation therapy but not in the breast carcinoma specimens from patients without angiosarcoma. In addition, MMP9 expression was higher in patients with postradiation angiosarcoma of the breast than in patients with non-radiation-associated primary angiosarcomas at non-breast sites. These results suggest that MMP9 may be a risk factor for and play a significant role in the development of postradiation angiosarcoma of the breast.