How could ultrasound be that far off?

Unfortunately, diagnostic imaging is not perfect. Even though it will give them a good idea of what they are dealing with, it's not until actual pathology is done that anything is definite. It should have been explained to you at the time, that pathology may up-stage or down-stage you depending on the results.

Hi Marie-Therese:

That is unexpected and your feelings are reasonable. Selena is right about the limits of imaging, and your surgeon is saying it does happen sometimes, so the pathology report could certainly be correct.

On the other hand, an error is not an impossibility. I don't want to get your hopes up, because it probably does not happen very often, but Tshire had a similar size difference between MRI and surgical pathology, and when she followed up, she found out it was an error. They accidentally measured the entire specimen, not just the tumor. Here is her post:

https://community.breastcancer.org/forum/5/topic/8...

You could check the actual pathology report for the size of the specimen (entire chunk of tissue removed), versus the size of the tumor, and the sizes of the margins. You may see something odd, and even if you don't, it is probably worth following up in some way with the surgeon and/or pathologist to double check given the degree of difference. You can also obtain an independent review of the pathology slides at another institution. That would not be unreasonable.

http://www.breastcancer.org/treatment/second_opini...

I haven't looked it up with respect to your particular size differential, but in general, size can affect the treatment recommendations under consensus guidelines. Size also affects the stage determination, which can affect prognosis, which plays into decision-making, so I think it is important to be accurate. Don't hesitate to follow-up in some manner.

BarredOwl

I was going to comment on my crazy experience but I see BarredOwl already summed it up for you. My surgeon acted like I was nuts but I kept pestering her to double check and she finally did and had to eat crow because the lab had indeed made a big error and it ended up being almost exactly the size the MRI had measured. My ultrasound measured 1cm, MRI was 1.3. MRI was right on target. NO harm in asking! Weeks later, when I got my pathology slides sent to MD Anderson they also noted my local lab's error and confirmed the 1.3 measurement. I really feel like that lab owed me an apology; it was extremely upsetting. Or at least some chocolates or something.

I saw your other post about Ki67/mitotic index, and we have almost the same Ki67/mitotic score- wow! Unusual. Please let me know what your doctors say about this.

My Oncotype ended up 20, very grey area. So because of my age I've opted to do 4 rounds of TC chemo. I'm cold capping so hopefully won't lose too much hair. Feeling pretty positive these days.

Let's keep in touch!