Sibling with breast cancer... concerns

My sister recently got dx with Lobular Invasive BC, stage 3, both progesterone and estrogen receptor positive. She is 40. She is going through chemo presently to shrink the tumor to a size where breast reconstruction is possible after mastectomy. She is upbeat despite baldness, etc.

My dr recently found a mass in my breast that has more than doubled in size in the last 6 months. It's about 2.5 cm. Had mammo which showed nothing except EXTREMELY DENSE breasts, so little is visible. I was sent for an ultrasound where 3 other areas were checked in addition to mass (dr's request). The determination was extremely dense cystic breasts but the mass was said to be "likely glandular fibrous tissue".. I think if it's grown that much that I should get it removed.. Ultrasound tech and radiologist said that based on u/s, that there was no indication for biopsy needed but I could follow up with surgeon if I wanted to.

Any thoughts? And how often do siblings develop lobular invasive breast cancer... sis is only 5 years younger than me. Thanks.

I met with a surgeon yesterday. She wants to remove and biopsy the lump. I will have it done Friday. The surgeon suspects lipoma though it did not show characteristics of lipoma on ultrasound. Will see. I just want it out since it's growing. Will post results when I have them. Thanks for your advice.

Had the surgery. Thank God I got a good nurse who could set a catheter well.

Didn't get to talk to the dr after the surgery, only before. She apparently told my hubby that it was somewhat fatty looking but wanted to wait for pathology report... so I assume it's not a lipoma then or she would have said it was. The scar is HUGE, a 3 inch incision that is stitched back together.

Sore. I hate the wait... hopefully will find out tomorrow sometime what the results are...

Follow up: developed a hematoma at the surgery site which ruptured Saturday all over my bed... blood everywhere... ruptured through the incision line... and now has refilled up. Back to dr tomorrow to get it drained and get a plan of attack...