There is a theoretical possibility of “needle tract implantation,” in which the tumor cells carried by the needle tip fall into the tract during the extraction of the puncture needle and develop into new lesions. In addition, it has been suggested that punctures can stimulate tumor growth and accelerate tumor spread.
Theoretically, any stimulation of cancerous tissue, including needling, excision, taking biopsies or other tests, as well as injections of anesthetic drugs, and even forceful rubbing and squeezing, could cause cancer cells to fall out and spread and metastasize. In fact, there are some shed cancer cells in the body itself (e.g. in the blood), most of which will be cleared by our immune system. Only when the immune function decreases, or when there are too many shed cancer cells that exceed our own ability to clear them, they will grow and eventually grow into metastatic cancer. Therefore, even if a small number of tumor cells are shed at the time of puncture, it is very difficult for metastasis to occur.
For thyroid cancer, there are no relevant case reports of needle tract metastasis in the professional community. The author’s center has done fine needle aspiration biopsies on thousands of patients over the years and has never seen accelerated spread after puncture.
This may be related to the characteristics of thyroid cancer itself. Most thyroid cancers are “lazy cancers” that develop very slowly, and even if a very small number of tumor cells are metastasized to surrounding tissue or bloodstream during the puncture, they will be removed, so there is no cause for concern.
However, as a precaution, if the puncture results are “malignant,” the doctor will arrange for surgery as soon as possible. In the meantime, during the time between the fine needle puncture and the surgery, try not to do anything that might increase the risk of tumor spread, such as not touching or rubbing the site of the thyroid puncture with your hands often.
Co-written by Dr. Yiming Cao, Cancer Hospital of Fudan University