Radiation‑induced pleomorphic liposarcoma after hypofractionated radiotherapy following breast‑conserving surgery: A case report and literature review.

Breast cancer is one of the leading causes of cancer globally. Radiotherapy following breast-conserving surgery is the standard treatment of breast cancer. Recently, hypofractionated irradiation comprising 42.56 Gy in 16 fractions was selected as a viable radiation therapeutic option. Radiation-induced sarcoma is the most prevalent secondary malignancy in patients undergoing radiotherapy after breast cancer surgery. Angiosarcomas are the predominant type of radiation-induced sarcomas, whereas liposarcomas have rarely been reported. The present report details an uncommon instance of radiation-induced pleomorphic liposarcoma that occurred 8 years after breast-conserving surgery and hypofractionated radiotherapy. The patient visited the hospital due to hardening of the tissue beneath the skin of the right breast. Ultrasonography revealed a hypoechoic mass in the lower part of the right breast containing internal blood flow. An excisional biopsy revealed that the tumor contained infiltrating spindle-shaped cells without a capsule containing pleomorphic cells. Lipoblasts were also observed and tended to differentiate into adipose tissue, leading to a diagnosis of pleomorphic liposarcoma. Immunostaining revealed negativity for cytokeratin AE1/AE3, ERG, MDM2 and S-100 protein; the Ki-67 index was ~20%. An enlargement resection involving a postoperative bed was performed because of close tumor margins. F-fluorodeoxyglucose positron emission tomography/computed tomography revealed pale accumulation of F-fluorodeoxyglucose in the right chest wall, which was interpreted as a postoperative change owing to the resection biopsy. The tumor was observed in the irradiated field with no distant metastases. Following extensive resection, the patient maintained a recurrence-free survival period of 3 years and 2 months, during which no adjuvant therapy was administered. Therefore, follow-up is necessary in patients with breast cancer treated with radiotherapy.