PD-L1-Expressing Radiation-Associated Angiosarcoma after Primary Breast Cancer

Radiation-associated angiosarcoma (RAAS) is a type of radiation-associated sarcoma (RAS) that develops at the previous field of radiation in breast cancer patients. Although several reports have suggested a poor prognosis for RAAS, the 5-year overall survival of RAAS is better than that of cutaneous angiosarcoma (CAS), suggesting that the prognostic factors of RAAS and CAS might be different, at least in part. In this report, we describe a case of RAAS, and employed immunohistochemical (IHC) staining of PD-L1 and MMP9 as well as periostin, IL-4, and CD163. Interestingly, IHC staining revealed that the RAAS in our case was positive for PD-L1 and negative for MMP9. Moreover, the predominant stromal factor of our case was periostin, suggesting that TAMs in the present case was not immunosuppressive, but an inflammatory subtype. These results might explain, at least in part, the better prognosis of RAAS compared to CAS.