In layman’s terms, recurrence or metastasis of cancer refers to the re-discovery of a tumor at the site of surgery or in another organ some time after surgery. Of course, this tumor must be of the same origin as the original tumor removed in order to fall under the category of recurrence or metastasis. If it is not from the same source, it is a different kind of primary cancer and does not belong to the discussion here. As mentioned above, newly discovered recurrence and metastasis originate from the cancer cells left at the time of radical resection. People are often confused why there is no basis for tumor metastasis before surgery, and the surgery removed the tumor, but metastasis appeared after surgery. Where are these metastatic cancers transferred from? This is the answer. These residual cancer cells are latent for a period of time and break through the defense of the body’s immune system again, which finally leads to recurrence or metastasis after surgery. Therefore, recurrence and metastasis, in terms of time, although the diagnosis is obtained after surgery, begin with intraoperative residual and preoperative latent. Simultaneous metastasis and heterochronic metastasis are often heard in clinical practice, which are only clinical classifications and are not fundamentally different. Simultaneous metastases are metastases that appear at the time of disease diagnosis, when the metastases are considered to be “simultaneous” with the primary site. Heterochronous metastases, on the other hand, are metastases that appear some time after the diagnosis of the disease, which is called not simultaneous. Postoperative metastasis is considered as heterochronous metastasis.