Complex Cystic mass

I am 34 years old and I got diagnosed with left breast cancer on June 2006 (Ductal carcinoma in situ, hormonal +). I had a mastectomy on september 2006 and I started chemotherapy on october 2006. I had T.A.C. chemo and I finished it on February 13, 2007. I am now taking TAMOXIFEN and baby aspirin.
I just have a check up with my obgyn and he prescribed a vaginal ultrasound and they jsut told me that I have a "COMPLEX CYSTIC MASS " on my left ovarian. I had my last period on december 2006 (due to my chemo) and I just have it back on 5/28/2007.
My vaginal ultrasound was taken on 5/21/07 and I got my period on 5/26/07.
Questions:
1. Can the cyst be a consequence of chemo, no period or the Tamoxifen?
2. Can the cyst/mass get expeilsed with my period?
3. Should I need to re do the ultrasound?
4. Is there a chance of cancer even after three months of finishing chemoteraphy?

Thank you so mcuh

[Annekathryn Goodman, M.D.]

Hi There,
The cyst could be just a cyst of ovulation now that you have started having periods again. It could also be from stimulation from tamoxifen. tamoxifen can act to stimulate ovulation. In fact, it was first developed as an infertility drug. These cysts are benign.
I would recommend a repeat ultrasound in 2 to 3 months
best wishes