Recurrence of carcinoma in situ in more than one year may be related to the differentiation degree of cancer cells, as well as the surgery and post-surgery treatment. Recurrence of carcinoma in situ after one year may be related to the differentiation degree of cancer cells. Generally speaking, less differentiated cancer cells tend to be more invasive and prone to recurrence after surgery, while more differentiated ones tend to be less invasive and less likely to recur after surgery. Carcinoma in situ of the breast is an early stage cancer confined to the epithelial layer, therefore, it is not prone to lymphatic metastasis or distant metastasis. Usually, it can be treated with simple mastectomy or breast-sparing mastectomy, and radiotherapy or no radiotherapy may be chosen according to the patient’s condition after the surgery. Different choices of surgical procedures and whether or not to carry out radiotherapy after the surgery may affect whether or not it is recurrent. If there is a recurrence of breast cancer in situ in more than one year, please follow the doctor’s instructions for treatment.