38 years female underwent suction curettage since one year for confirmed histologically vesicular mole. Bhcg showed plateau titre of 1000 , MTX was given for 6 cycles but after one year still a plateau of Bhcg 20 for nearly 2 months . us showed echogenic mass 1cm in fundoposterior segment of the uterus with low flow. the female is regular menstruating with non contraception. please provide differential diagnoses and management.