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Abstract

PRAME is normally restricted to germline cells involved in gametogenesis, primarily in the testis and placenta. However, PRAME has been increasingly detected by immunohistochemistry in a variety of malignancies, including carcinomas, melanomas, sarcomas, leukemias, and lymphomas. In several sarcoma subtypes, PRAME expression has been associated with higher metastatic risk and poorer prognosis. Angiosarcoma is an aggressive endothelial-derived sarcoma that can be challenging to diagnose due to morphological heterogeneity and frequent histologic overlap with other neoplasms. Tumors may range in degree of differentiation and mimic carcinomas, melanomas, lymphomas, or other sarcomas. Early or morphologically bland lesions may show minimal atypia, increasing the risk of misinterpretation as benign vascular proliferations or inflammatory processes. The lack of a definitive immunohistochemical marker to reliably distinguish angiosarcoma from borderline or benign angiomatous neoplasms further complicates diagnosis. In this study, we evaluated PRAME expression in radiation-associated breast angiosarcomas and non–radiation-associated primary cutaneous angiosarcomas. PRAME was scored based on percentage of positive tumor cells (0–4). Among 18 primary cutaneous angiosarcomas, 10 (56%) expressed PRAME, with an average score of 2.7. All 7 breast angiosarcomas (100%) were PRAME-positive, with an average score of 2.3. These results do not account for treatment stage, as prior studies suggest radiation exposure may alter PRAME expression. Because angiosarcoma prognosis is largely independent of cytologic atypia, PRAME expression may provide prognostic insight, similar to other malignancies where its presence correlates with higher metastatic risk. Moreover, because PRAME is presented on HLA class I–restricted cells, it represents a potential target for immunotherapy in angiosarcoma.