PRAME immunohistochemistry distinguishes breast secondary angiosarcoma from benign and atypical vascular lesions of the breast

Objective We examined the utility of preferentially expressed antigen in melanoma (PRAME) immunohistochemistry (IHC) in distinguishing breast angiosarcoma from benign or atypical vascular lesions (AVLs) of the breast. Methods There were 26 breast angiosarcomas (24 radiation related and 2 primary), 6 radiation-related AVLs of the breast, and 16 other benign vascular lesions of the breast retrieved from our institutional archive and stained with PRAME IHC. Results Twenty-four of 26 (92%) breast angiosarcomas were positive for PRAME with moderate to strong staining intensities (median HScore, 255 [range, 90-300]), while 0 of 22 benign or atypical vascular lesions of the breast were PRAME positive (sensitivity, 92.3% [95% CI, 75.9%-98.6%]; specificity, 100% [95% CI, 85.1%-100%]); c-MYC was positive in all angiosarcoma cases but showed weak staining in several cases (median HScore, 155 [range, 30-280]). PRAME was negative in 1 of 2 primary angiosarcomas and negative in only 1 of 24 secondary angiosarcomas of the breast. None of the benign or atypical vascular lesions was stained with PRAME. Conclusions It appears that PRAME expression occurs in a high proportion of radiation-related angiosarcomas and not in benign breast vascular lesions or AVLs. PRAME IHC is diagnostically useful in distinguishing benign from malignant vascular proliferations in patients with a history of radiation to the breast.