The ultrasound itself is not used to diganose the cancer. the stistical study shows that the cold nodules WITH internal blood flow and larger then 1 cm are generally having 22% risk to be suspected for the cancer. Presence of microcalcifications increases that risk to 23% [but your report did not indicate any].
Based of nodule size [more then 1 cm] and internal blood flow the biopsy must be performed to give the answer; also the lymph node can be biopsied as well.
In the past the fixed, firm and fast growing nodules were strongly suspected for cancer, now this conclusion can be made only after biopsy readings.
The most accurate way to determine whether or not there are any type of abnormal cells within the nodule is to have a biopsy of the nodule.