Hello, @mahdiheydarigmail, Welcome to Mayo Clinic Connect. I want to reach through the computer to give you a calming hug. Your mother is young at 58 and can get through this! Osteosarcoma in the jaw, according to information I’m providing below, generally doesn’t metastasize outside the jaw bone and it produces higher survival rates. So that is a positive takeaway.
https://moffitt.org/cancers/sarcoma/faqs/about-osteosarcoma-of-the-jaw/
However, your mom will most likely require surgery to remove the tumor with a followup of chemo and/or radiation. This is not going to be easy for her…cancer never is. But I’m guessing your mom is a very strong woman and she will push through this.

What you can do right now is to remain calm and positive for her and for yourself. Truly, I understand how difficult this is. I am a surviver of a very aggressive cancer so I know that there is always hope…and I’m a decade older than you mom! ☺️ Getting through our cancer treatments is a challenge but worth the effort to persevere.

It will help your mom if you or someone close to her will accompany her to all appointments to take notes. Sometimes when the doctors talk it is overwhelming with all the information. So having someone else along to listen and make notations for later is important.
You can bring your own list of questions for the doctor as well. Let’s wait for the diagnosis to return and then we can talk about this more, ok?
You just gained a new family here on Connect so you’re not alone. Family support is important at a time like this. Do you have any siblings or relatives nearby?