RESUMO
Background: Ductal carcinoma in situ within a breast fibroadenoma is a rare malignancy with an incidence of only 0.02-0.125%. Imaging of low-grade ductal carcinoma in situ within a breast fibroadenoma shows no specific presentation. Therefore, pathology and immunohistochemistry are required for definitive diagnosis. Surgery is currently considered to be an effective treatment. There is no uniform clinical standard for postoperative adjuvant radiotherapy. Case Summary: A 60-year-old female patient underwent excisional biopsy on October 19, 2022. Pathology and immunohistochemistry confirmed the diagnosis of low-grade ductal carcinoma in situ within the fibroadenoma. Subsequently, breast-conserving surgery and sentinel lymph node biopsy were performed under general anesthesia with tracheal intubation, and no cancer metastasis was observed in the sentinel lymph nodes or incisional margins. Conclusion: Low-grade ductal carcinoma in situ within a breast fibroadenoma is an extremely rare malignancy, and clinicians should be familiar with its clinicopathological features and treatment methods. Multidisciplinary joint treatment is recommended to maximize the benefits to patients.