Core Biopsy Negative - Do false negatives occur?

Hey

I am 31yo in July and in early January I noticed a really large hard lump under my nipple and areola, so I asked my specialist physician (I am type 1 diabetic) for a referral to have it scanned. The Radiologist did a sonar, followed by a mammogram and gave me a BI-RAD of 4B in the suspicious range, and did a US guided core biopsy. He wasn't all that happy with the 4 samples he too, as they were small, because he battled to get a sample. The lump is as hard as a marble, so he had to put his full body weight into getting the needle in, then it got stuck as he pulled it out. this happened all 4 times. My Specialist sent me the results 2 days later, and everything came back as benign.

However, the lump seems to be increasing in size and my actual nipple is changing. Yesterday, I sent the results to a breast specialist I had previously seen (for my extremely dense diabetic breasts) and she immediately responded that she wants to see me this afternoon, and I must be honest, I am extremely anxious.

Are false negatives on a core biopsy a thing - I have had a really bad feeling about all of this since the start of this.

Any and all feedback would be much appreciated!