Bowel cancer? Pancreatic?

Hi guys bit of a complex story. Basically my mum was admitted into hospital due to ascities (fluid on the tummy) after a month of investigations it was found she has extensive bone mets doctors are unable to locate her primary they say. Although a pet scan showed a mass in her bowel (caecum) but colonoscopy biopsy of polyp was negative and they didnt go any further than that so possibly could have been missed.. her ca 119 markers are extremely high and Cea high. She has blood in stools every now and then, constipated then loose and incontinent.. All classic signs of what we would expect from bowel being her primary. However a lymph node biopsy along with those raised markers has suggested it is from the upper gastrointestinal tract which has now lead doctors to believe it is pancreatic or bile duct but they cannot officially diagnose but wont do anymore testing. A CT / PET showed pancreas clear? Upon researching she is not symptomatic to these cancers what so ever so we are confused as to what to do next. She has undergone 2 rounds on chemo gemcitabine and abraxane i think.. and tumor markers have raised from 6000 to 8000 in ca 119. So confusing we cant help but feel they are mis diagnosing, currently in the process of seeking a second opinion but of coarse that takes time and we are at our wits end trying to understand this. Any help/ experiences suggestions will be highly appreciated. Thanks so much