Radiation-Associated Angiosarcoma of the Breast: A Case Report with Review of Reported Cases in Japan

INTRODUCTION: Radiation-associated angiosarcoma of the breast (RAASB) is an extremely rare but serious complication that can occur several years after breast-conserving surgery and adjuvant radiotherapy. Owing to its rarity and nonspecific cutaneous manifestations, the diagnosis of RAASB is often delayed. There is no established treatment for RAASB, and its prognosis remains poor. CASE PRESENTATION: A 63-year-old woman developed progressive breast edema 14 years after breast-conserving surgery with axillary lymph node dissection and adjuvant radiotherapy for invasive ductal carcinoma. Two years later, she presented with breast masses with purpura and biopsy-confirmed angiosarcoma. Wide mastectomy with skin grafting was performed, followed by weekly administration of adjuvant paclitaxel. The patient remained recurrence-free for 12 months postoperatively. CONCLUSIONS: RAASB can develop long after breast-conserving therapy and may be preceded by subtle skin changes or persistent breast edema. Long-term follow-up and patient education are essential for patients who have undergone breast irradiation. Early imaging or biopsy should be considered when breast lymphedema is observed.