Clinically known as endometriosis, it is a specific disease that is essentially benign but exhibits some of the behaviors of a malignant tumor, such that it can grow and thrive in areas far from the uterus such as the lungs, nasal cavity and skin, while surgically removing the lesion and then quickly recurring in situ. Medical doctors and scientists have so far failed to find the exact cause of the development of endometriosis, and several hypotheses have been proposed to explain it. The “retrograde flow of menstrual blood theory” refers to the flow of menstrual blood through the fallopian tubes to the pelvic cavity, where the endometrial cells in the menstrual blood seed the ovaries and peritoneum to form lesions. The “somatic epithelial metaplasia theory” refers to the transformation of tissue cells in the pelvic cavity into endometrial cells to form lesions when stimulated by certain factors. The “vascular-lymphatic metastasis theory” refers to the metastasis of endometrial cells into the blood vessels and lymphatic fluid of the uterus, which then metastasize to sites far from the uterus, forming lesions in the lungs, nasal cavity, skin, etc. These are the three mainstream hypotheses, each of which can explain some clinical manifestations. However, because the manifestations of endometriosis are so diverse, each hypothesis cannot fully explain all the symptoms of the disease, so medical doctors and scientists are still trying to explore the research.