The most common copy number variant was a copy number loss of CDKN2A/B (26% of cases), followed by MYC amplification/copy number gain (22% of cases); a total of 67% of the cases involving MYC amplification/copy number gain were radiation-associated angiosarcomas of the breast arising after treatment for breast carcinoma. The gene discussed is CDKN2A; the disease is breast carcinoma.