BI-RAD 3

If it were me I would be asking for a referral for genetic counseling rather than oncology. While a grandmother can raise our risk somewhat, if your mother or a sister have not been diagnosed before 50 your risk may well be average. Most women have heterogeneously dense breasts (50-75%). It is only very dense (75-100%) that is considered more of a risk. Since you have already had an MRI in addition to mammogram & ultrasound they are telling you with pretty good confidence that your risk with whatever is going on is less than 3%. Most breast discharge is hormonal and benign too. Having unnecessary biopsies can cause scarring that leads to more biopsies.

You can't compare your situation with anyone else's because you don't know all the details. With all three diagnostic tests it is very highly unlikely you have anything serious going on. If anything, MRIs tend to produce false POSITIVES, not false negatives. Many women have been "pinkwashed" by the constant Komen campaigning. Many women also think they are higher risk than they are. Again, if you are very anxious, a counseling session with a geneticist might help put your mind at ease. Fewer than 10% of breast cancers are genetic.

Also remember that you are posting on a breast cancer board. All the thousands of women in your situation who had their clear six-month follow-ups are out there living their lives and not hanging around here.

No, no! Nobody's upset! Just trying to reassure you that you may be alarmed unnecessarily and to make some suggestions.

No one is ever comfortable with the words "Probably Benign" but that's the unfortunate choice of words that they've used as the official definition of a BIRADs 3:

BI-RADS 3

Probably Benign Finding - Initial Short-Interval Follow-Up Suggested:

A finding placed in this category should have less than a
2% risk of malignancy.

It is not expected to change over the follow-up interval, but the radiologist would prefer to
establish its stability.   Introduction to the Breast Imaging Reporting and Data System

You mention that the BIRADs on your MRI was a BIRADs 3. Do you have the BIRADs ratings for your mammogram and ultrasound?

Because BIRADs ratings are subjective, with a BIRADs 3 it can make sense to get another opinion, either from another radiologist or from a breast specialist (a breast surgeon).  Did you request that imaging be sent to a surgical oncologist (which would be appropriate) or a medical oncologist (which would not be appropriate)? 

If the second opinion agrees with the BIRADs 3 assessment, then as MelissaDallas suggests, personally I would not push for a biopsy.  An biopsy can lead to more problems down the road so you really don't want to have one unless it is recommended. 

Also, as Melissa mentioned, keep in mind that this is a breast cancer discussion board.  So yes, you will find a number of women here who had BIRADs 3 imaging who did end up with a diagnosis of breast cancer.  In fact it may appear that most BIRADs 3s have ended up with breast cancer, just as your teacher did.  But that's because it's mostly women with breast cancer, or who are high risk, who hang out here.  We are not in any way an representative sample.  Here are a couple of studies that are more representative of all BIRADs 3 situations:

"Among all subjects whose tumors were assigned a BI-RADS 3 category
either at screening mammography or after additional work-up, nine of
1114 (0.81%) were found to have cancer."  http://www.ncbi.nlm.nih.gov/pubmed/21502382

"Of 2662 participants, 519 (19.5%) had 745 BI-RADS category 3 lesions... Six malignancies (0.8% of BI-RADS category 3 lesions...) occurred in five (1.0%) of 519 participants"  http://www.ncbi.nlm.nih.gov/pubmed/23962417

Both studies had a 1% or less rate of malignancy.  This means that if you hear from 5 women here who all had BIRADs 3s and ended up with a diagnosis of breast cancer, there are 495 other women who are not hanging out here who had a BIRADs 3 and were not diagnosed with breast cancer.

Lastly, as for your risk level, having a grandmother who had breast cancer, even at a young age, potentially doesn't increase your risk at all, but it would be advisable to get genetic counselling so that you can understand that better, rather than just assume that it puts you at high risk.  You also should know that 74% of women in their 40s have dense breasts - it's a normal condition for pre-menopausal women.  The following study of over 7000 women found that "a majority of patients
(57%) between the ages of 40 and 49 years had high-density breast
tissue (i.e. heterogeneously dense), and an additional 17% had very-high-density breasts (i.e. extremely dense)." The Relationship of Mammographic Density and Age: Implications for Breast Cancer Screening   The average woman in her 40s has only a 1.47% chance of developing breast cancer during the entire 10 years of her 40s; in other words, the annual risk is just under 0.15% per year.  This figure is an average for all women in their 40s, so it includes the 74% who have dense breasts and even those who have a strong family history.  Your own risk might be a bit higher than this average since you have both of those risk factors, but overall your risk remains very low. http://www.cancer.gov/cancertopics/factsheet/Detection/probability-breast-cancer

With an abnormal mammogram and ultrasound and a BIRADs 3 on your MRI, getting the second opinion is a good idea.  But don't scare yourself into thinking that you are very high risk and this is likely to be cancer.  You most likely aren't high risk at all, and it's most likely not cancer.