Found blood in urine with some enlarged lymph nodes, what tests need to done?

My question is regarding my mother; she is 62 yrs. old with no previous medical concerns, non-smoker, and non-drinker. However she does not regularly see a doctor for annual check ups. Just this month she cancelled a trip over seas due to finding blood in her urine. Ever since then she has had all kinds of testing done including: a physical with breast exam, blood work (Glucose-fasting, cholesterol, TSH, CBC), urinalysis, mammogram and bone densitometry, seen an OBGYN and had a pap, and a pelvic/abdominal ultrasound. Out of all these tests the bone densitometry showed signs of osteoporosis and the abdominal ultrasound showed some enlarged lymph nodes, everything else was normal including WBC. So her doctor recommended an abdominal/pelvic CT scan to “rule out malignancy” we did the CT and everything was normal except “at least 3 enlarged lymph nodes within the root of the small bowel mesentery the largest measuring 3.3x 1.8 x 2.9 cm. There is no pelvic or inguinal lymphadenopathy by size criteria. No ascites” –this is quoting the radiologists report. In this report he recommended we follow up with a chest CT to look for any other lymphadenopathy or overt intrathoracic malignancies and also that we biopsy the abdominal lymph nodes by ultrasound guided fine needle aspiration. So we did the chest CT and it came back as a normal chest CT with “no signs of intrathoracic lymphadenopathy”. Now we are booked in for the Fine needle biopsy on Thursday. My question is have we missed looking into anything that may have caused these 3 enlarged lymph nodes or could this be a purely isolated case? Would a PET scan help diagnose anything lurking that we may have missed? I understand that lymphoma could be a possible diagnosis and that is why they are doing the biopsy but does lymphoma generally start in the abdominal lymph nodes?
Thank you very much