Post menopausal rt. ovaian cyst.

It was diagnosed incidentally in Feb 2017. Since then repeated usgs have been done at an interval of 3months. Size of cyst is increasing. In latest usg (dated 8-09-18) pelvis+ tvs reports findings are :Rt. Ovary occupied by multiseptated avascular cyst with thin sleeves of stroma around it. This measures 60×53×56 mm , volume 95cc. Lt ovary: measures 32×17×31mm, volume 9.2cc and shows septated cyst of 19×16mm. Previous usg (dated 6-06-18)s/o Rt ovary: shows a well defined round anechoic cyst with moderately thick internal septae (1.9mm) within. It's volume measures 47cc. Lt ovary :normal in size and echotexture. Thus , size of cyst has increased and it has become B/L . What is the treatment? What are the chances of malignancy?