what kind of breast lumps don not show up on mamo or u/s

I have a lump in the left breast behind the areola. This is felt by both myself and PCP. Went to have mamop and u/s and both of the techs could feel it but both proceedures could not detect the lump. It is larg/hard and not moveable. It is easly to feel. I did have surg on that side but I don't think it is scar tissue. Beast cancer in 2 maternal aunts/ 2 maternal cousins.
Will see PCP this week. What would prevent the lump from showing up on mamo or u/s

[Cleveland Clinic]

Dear bjkatz:  If a lump is easily felt and of concern to the doctor, a surgeon could do a fine needle biopsy without any images.  You might discuss next steps with the doctor who examined the lump.

[KeyD]

I wish I had an answer for you because my story is the same. My insurance just declined an MRI, so I don't know what's next.