Scattered fibroglandular tissue is a combination of glands and fibrous tissues which is "normal" and many women have this condition. It describes the tissue as lumpy, or dense. Since you have dense breasts, which make mammogram readings more difficult, your Doctor/Radiologist is recommending an Ultrasound to see things more clearly particularly concentrating on the nodule in your outer left breast. If nothing suspicious is detected, your doctor will let you know when a follow-up is needed to make sure that no changes have occurred. However, if the Ultrasound test shows that the nodule is doubtful, a biopsy might be recommended because this is the only way to know for sure what this lump represents.
Please call your Doctor, who has your complete Mammogram report and who can explain to you all the details concerning the findings.
Best wishes and hoping that there is nothing there to worry about....
Thank you very much for the quick response.