Hi I have teratoma removed (approx 11cm) on my Right ovary 2 years ago. A regular half yearly ultrasound has been done. Recently, there is a 3.1x3.0x2.3cm cyst (simple) is found on my right ovary, estimated volume of 30cc. endometrial thickness is 12mm which is in secretory phase. uterus measures 7.8x4.2x3.4cm. Fyi, I was on the very last day of my period when I had the ultrasound. I do notice that my period brought forward a week since the last two months. I am 33 years old female, sexually inactive. What kind of test should I do to ensure whether the cyst is malicious? Much appreciated.