###Human: Kindly explain non-FDG avid in a PET scan of a breast cancer patient. ###Assistant: Hi. I can understand your concern regarding the new findings on CT PET Scan of your mother. She is having multiple bony metastases proven radiologically and pathologically. The generalized mesenteric and omental haziness with raised tumor markers Ca 125 / CEA, these findings raises suspicion of peritoneal involvement. But, there is no clear nodule or mass found in the abdominal cavity. So she needs a close follow-up and further investigations.  She has proven bone metastasis as confirmed pathologically and radiologically (CT scan) with out uptake of FDG. Non FDG avid means her some bone metastasis have not taken up FDG. Usually, tumor and the metastatic site takes up FDG But here bone metastasis has been confirmed already by CT scan and biopsy. At this stage, I would suggest you discuss with your oncologist for a possible laparoscopic evaluation of the abdomen (peritonuem, omentum, and mesentery). It will show any visible suspected lesion in the abdomen and biopsies can be taken from any suspicious lesions or she can be put on close follow up and a PET CT and tumor markers can be repeated after two months. They should also drain the abdominal fluid and send it for analysis (cytology for malignant cells). Also, she may need transvaginal ultrasound that is very sensitive to detect any ovarian tumor. Because ovary is one of the common causes of peritoneal and omental involvement. She may also need to do an MRI whole spine as there are multiple vertebrae (spine) metastasis. There is a risk of spinal cord compression and MRI can detect it early. Did she have a previous surgery of the uterus or ovaries or any abdominal surgery?