secondary malignancy?

Hi,
I am a 31-year old woman. I went to the doctor a few weeks ago because I was having pain near my tail-bone. I thought I had injured it while biking. Well, an MRI revealed a soft-tissue mass in that area. I had a cat scan yesterday, and the doctors told me that there is a soft-tissue lesion both in my gluteal muscle and in my sacral bone (but mostly on the left side). I have been referred to a neuro-surgeon, but the first appointment I could get is two weeks away. I am very confused. I can definately feel the mass growing. I had radiation and chemo as a toddler for a childhood tumor (ganglioneuroblastoma) in my back-side/muscle. My doctor said this new growth is probably due to the radiation treatment.

Has anyone had experience with this? What is the prognosis for a secondary malignancy? Should I get a second opinion?