please help me to understand

I'm in Canada and I always have a BIRADs rating on my reports. So the issue with not having a BIRADs rating is obviously specific to the place that you had your mammo done; it's not because Canadian radiologists don't use the BIRADs system. They do.

It seems that the reason you have no follow-up scheduled is because everything looks perfectly fine.  In about 75% of cases where there is a concern or a follow-up, all that's necessary is further imaging.  At that point it's evident that there are no concerns so no more action or follow-ups are required.

About what your report says:

the breast are composed of approximately 50% fibroglandular density  That's right at the top end of the second category of breast density.  Breast density of 25% - 50% is called "scattered fibroglandular density".  It means that there are some areas of the breast that are dense but the entire breast is not.  Depending on your age, this might actually be less breast density that most women your age.  Younger women tend to have denser breasts and I believe that the majority of women in their 40s and younger have "heterogeneously dense breasts" - this is breast density of 51% - 75%. The highest category of density is "extremely dense breasts" - this is 76%+ density.  So with 50% fiboglandular density, your breasts are a bit dense but not particularly dense.  This means that screening shouldn't be affected by your breast density.  So that's good. 

the parenchymal pattern is symmetric between both breasts.  This just means that your breast tissue looks the same in both breasts.  That's great.

No suspicious mass is identified. specifically no focal abnormality is seen in the upper outer quadrant. as the patient cannot feel any palpable abnormality, an ultra sound examination was not performed. there are no areas of architectural distortion or suspicious cluster of microcalcification  Basically that says that they looked for masses and any other type of abnormality in your breasts and particularly the upper outside quadrant of your breast (is that where your family doctor felt something?) and they found nothing of concern.

As for why there no ultrasound was done, according to the information you provided, that's because the radiologist (and the surgeon, it seems) could not find any palpable lump. So there was nothing for them to check with the ultrasound.

Here's what I think it all means. Normal breasts often feel lumpy. Your family doctor is not an expert on breasts. What felt concerning to your family doctor might well have been normal breast tissue. The mammo didn't find anything and the surgeon couldn't feel anything. 

My advice is to take that as being good news.  I'd also suggest that you do regular monthly breast self exams, so that you know if you feel any changes in the area that is of concern to you. If you do feel changes - if you start to feel a more defined lump and if it seems to be getting larger, then go back to your doctor.  Don't check more than once a month because you will drive yourself nuts and you will end up feeling things that aren't there. And do the BSEs at the same time in your cycle every month, ideally right after your period ends.

It sounds like you got really good news. You are worried because you wonder if your family doctor was right, and I understand that. But it's a lot more likely that the films and the surgeon are right and that you have nothing to worry about.