pancreatic cyst 28cm x 15cm

Hi, I was in hospital a couple of weeks ago when an ultrasound scan showed up a large pancreatic cyst of 28cm x 15cm which appears to be originating from the pancreatic tail.  Prior to the finding I had been experiencing abdominal discomfort, excessive gas and indigestion.  I have never had pancreatitis, I do not drink alcohol apart from one glass at Christmas, I have never had any abdominal trauma and the only abdominal surgery I've had is c-section in 1994.  I am 41 and also in my first trimester of pregnancy.

A second ultrasound was performed and the radiologist said that the cyst was multilocular and that in his opinion it looked benign.

I saw the gastroenterologist last week.  He said that he felt that because the cyst is so very large that it must have been there for a very long time which leads him to believe it is not malignant.  He also pointed out that my symptoms are mild and I am not unwell or losing weight.  He has scheduled another ultrasound for next week to see if they can get a more detailed picture and to see if they can get a definite on it coming from the tail.

My argument is that with a cyst this large I surely would have felt changes a fair while ago.  In actual fact the discomfort etc only started about 6 - 7 weeks ago and I have also gained around 7lbs in weight during that time also (query - could this be the weight of the fluid within the cyst).  I have found very little information about cysts as large as mine, the info I have found all point towards surgical removal due to risk of pre-cancerous or cancerous cells.

My biggest worry is that an ultrasound is not really the best diagnostic tool with regard to differentiating between a pseudocyst or a possible malignant cyst.  Everything I have read says this.  They cannot do a CT or MRI scan at the moment because of the risk to the baby and the specialist says he doesn't really want to do an endoscopy or stent either because of the risk of infection.

Any input would be much appreciated.  I'm obviously very aware of wanting to reduce any risks to my baby but I also don't want to leave testing until it's too late.  Oh and my ob-gyn has already said that with the cyst insitu there is no room for the baby to grow.  The gastro and the ob-gyn will discuss things after my next ultrasound apparently.

Sorry for the length of post.