Nearly 10% of patients will experience recurrence after mastectomy for early-stage breast cancer, and once recurred, the prognosis varies widely by type and subtype of recurrence, often requiring multidisciplinary treatment. One type of recurrence, called “isolated recurrence”, has a relatively good prognosis and often requires multidisciplinary treatment based on radiotherapy. 1. What is an isolated recurrence? Isolated recurrence after mastectomy refers to the presence of local-regional recurrence, but no distant metastases are found within three months of the diagnosis of recurrence. Local recurrence refers to the recurrence of invasive carcinoma in the ipsilateral chest wall, which may manifest as skin or subcutaneous nodules, skin erythema, or skin ulcers in severe cases; regional recurrence refers to the recurrence of invasive carcinoma in the ipsilateral lymphatic drainage area, including the ipsilateral axilla, internal breast area (parasternal), and supra- and infraclavicular area, which manifests as enlarged lymph nodes. In terms of the frequency of recurrence, chest wall recurrence is the most common, followed by supra- and infra-clavicular region, and again by internal mammary region, while axillary recurrence is relatively rare. 2.What are the characteristics of the time course of isolated recurrence? Firstly, from the time course of recurrence, the peak time of recurrence is 2-3 years after mastectomy, and nearly 80% of recurrences occur within 5 years after mastectomy. However, the time course of recurrence varies greatly among different molecular subtypes of breast cancer, and the proportion of recurrence within 5 years after surgery is much higher in receptor-negative (including triple-negative and HER2-positive subtypes) than in receptor-positive patients; in other words, receptor-positive patients will still recur 5 or even 10 years after surgery, showing an endless trend. In addition, the status of axillary lymph nodes at the time of mastectomy also affects the time course of recurrence, with those with positive axillary lymph nodes recurring earlier than those with negative axillary lymph nodes. 3.How is an isolated recurrence diagnosed? Most isolated recurrences are detected during regular follow-up, and a few are discovered by the patient by chance. Most skin nodules or erythema can be detected by visual observation; subcutaneous nodules or superficial lymph nodes can be detected by palpation. During follow-up, the doctor will also give the patient regular CT or ultrasound examinations of the chest to help detect deeper lesions, such as lymph nodes in the internal breast area, subclavian area, etc. Once abnormalities are found on physical examination or imaging, pathological confirmation should be obtained whenever possible, including excisional biopsy, fine needle aspiration or coarse needle aspiration. In addition, other distant sites such as lung, liver, bone and brain must also be examined to exclude distant metastatic lesions. 4. How to treat isolated recurrence? Compared with recurrence with distant metastases, the prognosis of isolated recurrence is relatively good and potentially curable, so it should be treated actively. As far as the means of treatment is concerned, for patients who have not received radiotherapy in the past, radiotherapy must be used as an essential local treatment regardless of whether the recurrent lesion is surgically resected or not. Good local-regional control can be obtained through local-regional radiotherapy, with a 5-year local control rate of more than 70%, and the application of paclitaxel or capecitabine synchronized chemotherapy can further improve local control. In addition to local treatment such as surgery or radiotherapy, systemic treatment needs to be given in combination with different subtypes, such as endocrine therapy for receptor-positive, trastuzumab for HER2-positive, and systemic chemotherapy for triple-negative. 5.What should I pay attention to after treatment of isolated relapse? Although good local control can be achieved after treatment of isolated recurrence, there is still a possibility of recurrence after treatment, including recurrence at locally treated sites and distant metastases, so it is important not to take it lightly. After treatment, close follow-up is still necessary, including regular physical examination, imaging examination and tumor marker examination. During the follow-up, it is necessary to pay close attention not only to the reappearance of invasive cancer in the localized-area of the chest wall, but also to the metastatic lesions in the lung, liver, bone and brain.