Lump can't be seen on mri

I was sent for an mri on 2 lumps high inside the vaginal wall. An ultrasound showed what looked like 2 pea sized  cysts. They've have got slightly bigger since first noticed a year ago so I was sent for an mri. The lumps can't be seen on an mri so they've made a follow up check for an examination in 4 months. They speculated it could be a blocked gland but also said there is no way to ever be certain something isn't cancer without lab test. He also said the removal would be very tricky and risky and cause side effects later. Not feeling reassured. Has anyone experienced this?