Breast cancer is one of the most prevalent malignancies in women. Its main cause of death is the recurrence and metastasis of breast cancer. It is particularly likely to recur within the first 5 years, accounting for almost 75% of the overall recurrence rate. The formation of metastatic foci is a continuous and complex process that begins early in the growth of the primary foci. The entry of tumor cells into the blood circulation is the basis for metastasis. The metastatic foci are formed through multiple complex mechanisms. Therefore, the detection of circulating tumor cells (CTCs) plays an important role in predicting metastasis. In August 2004, foreign scholars evaluated the use of CTCs in breast cancer patients and concluded that the median progression-free survival rate was lower in patients with elevated CTCs at the first S visit. A study of metastatic breast cancer published in 2006 in provides ample evidence that CTCs are an accurate indicator of the effectiveness of treatment for breast cancer. Levels of CTCs in breast cancer patients correlate with tumor stage, with elevated levels of >5 being indicative of a higher likelihood of metastasis and predicting a poorer prognosis for the patient. Compared with the traditional tumor marker CA-153, and imaging tests such as ultrasound, MRI and PET-CT, CTCs have higher reproducibility and sensitivity. When the lesion is only 0 or 5 mm in size, it can be reflected in time. The continuous detection of CTCs allows early assessment of treatment effects and, accordingly, a timely shift to a more effective treatment plan and improved yield. The FDA has approved a system called CellSearch for the identification of breast cancer metastases, which can correctly and effectively identify and count CTCs in blood samples. Venous blood is sufficient. Most of the patients eliminated their doubts and avoided over-treatment, and a few patients with CTCs >5 or more were promptly treated with salvage therapy and adjusted treatment plans. We deeply appreciate that CTCs examination is a new tool emerging in the diagnosis of breast cancer recurrent metastasis, and their appearance has greatly improved the accuracy of breast cancer recurrent metastasis examination. They provide a powerful tool for prognosis, evaluation, and individualized treatment of tumor patients.