Dad, 76, had prostate removed in 2015. routine doc appt has him scheduled for ultrasound for primary malignant neoplasm of prostate. is this serious? he seems fine and not complaining of anything?

A reason is needed on the request to order a test , and that diagnosis might have been used. It is important to know ultrasound of what area was ordered. Your dad or you can ask the MD. When seeing an MD always ask why a test was ordered and what the MD expects to learn from it.

Any surveillance test will list the main condition as the reason for the test even though it may not be known as being active at the time. It is more of a coding/billing message, feel free to confirm with ordering doc for peace of mind.