A Case of Undifferentiated Sarcoma that was Difficult to Differentiate from Intra-breast Recurrence after Breast Cancer Surgery

Abstract

We report a case of undifferentiated sarcoma that arose approximately 14 years after partial mastectomy for breast cancer. The patient was a woman 40-years-old who underwent left breast partial mastectomy and sentinel lymph node biopsy for left breast cancer, cT2N0M0 stage IIA. The pathological findings included invasive ductal carcinoma of the breast with a tumor size of 1.8 × 3.0 cm, n0, lymphatic invasion (ly0), venous invasion (v0), and no positive lymph nodes (n (0/4) ). Estrogen receptor (ER) and progesterone receptor (PgR) were positive, HER2 was 1+, nuclear grade was 1, and the Ki-67 index was 3.2%. Surgical margins were negative. Postoperative adjuvant therapy included radiation therapy to the remaining breast and endocrine therapy, and the patient remained free of recurrence. Approximately 14 years after surgery, the patient noticed a lump in the left breast, which was diagnosed as local recurrence of breast cancer. Upon re-excision, the diagnosis was made as radiation-induced soft tissue sarcoma. Due to early detection, the tumor was completely resected through surgery, and the patient is currently without recurrence. Radiation-induced sarcoma is a very rare condition with a poor prognosis, and thus there are no established treatment methods for postoperative care or for advanced cases. It is important to keep this condition in mind during follow-up after breast cancer surgery to ensure early detection.