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Objective:
Radiation-associated angiosarcoma of the breast (RAASB) is a rare type of secondary angiosarcoma with a poor prognosis that often presents as skin changes in women following breast cancer radiation treatment. The purpose of this study was to evaluate the pre-treatment MRI characteristics of RAASB.

Materials and Methods:
An Institutional Review Board (IRB)-approved single-center retrospective study of patients diagnosed with RAASB was performed. Pre-treatment breast MRI examinations were evaluated by dedicated breast imagers. All examinations were assessed for skin enhancement, intraparenchymal enhancement, disease focality, size, maximum skin thickness, axillary lymphadenopathy, T2 characteristics, and enhancement characteristics, including enhancement kinetics.

Results:
In total, 38 patients with a diagnosis of RAASB of the breast were found, and 24 of those patients underwent pre-treatment breast MRI assessment. 91.7% (22/24) had skin enhancement. 45.8% (11/24) had intraparenchymal enhancement, and multifocal disease was found in 70.8% (17/24). The average maximal size of enhancing tissue across patients was 4.39 cm (SD = 3.8). The average maximal thickness of enhancing skin in patients with cutaneous disease was 0.75 cm (SD = 0.32). No lymphadenopathy was noted in any patient. 95.8% (23/24) demonstrated high T2 signal. 58.3% (14/24) demonstrated washout enhancement kinetics. The enhancement pattern was most often heterogenous in 54.2% (13/24) and homogenous in 33.3% (8/24).

Conclusion:
In our cohort, the most common MRI findings of RAASB of the breast included frequent skin enhancement, almost universal high T2 signal, often multifocal disease, and heterogenous enhancement. RAASB is an aggressive and rare malignancy that demonstrates unique MRI characteristics.