Mature teratomas are benign tumors with a low chance of recurrence. However, immature teratomas are malignant tumors and have a relatively high chance of recurrence after surgery. 1. Mature teratoma: it can occur at any age, mostly in 20~40 years old, and the recurrence rate is very low if surgery is done in this case. However, if it occurs in postmenopausal women, about 2%~4% of the patients will develop malignant changes, therefore, this case should also be closely observed. 2. Immature teratoma: it is mostly seen in young patients, mostly 11~19 years old. The recurrence and metastasis rate of this tumor is high, but after recurrence and reoperation, immature tumor tissue can be seen to be transformed to maturity, i.e. malignant degree reversal phenomenon, which is its unique characteristic. Most teratomas are mature and cystic, while a few are immature and solid. Mature teratomas account for more than 95% of ovarian teratomas, and immature teratomas account for 1% to 3% of ovarian teratomas.