You asked if most lumps are cancerous. The answer is no...most are benign. Only about 20% are cancer. It is a good thing your MIL is having a mammogram. That is usually where they start. They also may ask for an ultra sound and a biopsy. What you/she needs to do is take one step at a time.
Please feel free to ask any questions...this is a group of very knowledgeable women...
I'm sorry it turned out to be BC. My tumor was kind of the shape of hers, too. Is she having a mastectomy or lumpectomy? The reason I ask is because I had a lumpectomy, only to have the surgeon discover more cancer once he was in there. Since we had not had a conversation about 'what ifs', I had to have a 2nd surgery (mast) 3 weeks later. Make sure she discusses with the surgeon all the possibilities. I was in too much of a daze to even think to ask anything.
Go ahead and have that big cry. It does help. Then you will be able to be strong for your MIL. She is a very lucky woman to have you for a DIL! You care for her so much and that shows. Good luck!
Dorri: Sending lots of prayers for your mil and entire family. Yes, she will need some help for a week or so. She won't be able to lift her arm so she will need to be sure and have tops or gowns that button rather than go over her head. Also, she may need some help w/ her hair and shower. I found that I wasn't comfortable in my bed the first few days, so I slept in the recliner w/ lots of pillows to help prop me up. Allow her to do what she feels like doing but don't let her lift anything heavy. Nothing over the weight of a guart of milk the first couple of weeks.
Please let us know how she does.