You're simply wrong. Again, cancer is malignant by definition. And again, you seem to be confusing "cancer" with "tumor" -- your description applies to the latter, not the former.
You can label a slow-growing tumor as "not-cancer" if you want, for psychological reasons, I guess; "cancer" just sounds scarier. Some slow-growing "not-cancer" tumors are faster than others. It's a sliding scale, not a dichotomy.
https://jamanetwork.com/journals/jamaoncology/fullarticle/27...
"Malignant tumors are cancerous (ie, they invade other sites)."
https://www.cancer.org/cancer/understanding-cancer/what-is-c...
"Tumors are lumps or masses of abnormal cells (neoplasms) that can be malignant (cancer) or benign (not cancer)."
https://www.merriam-webster.com/dictionary/benign
"of a mild type or character that does not threaten health or life especially : not becoming cancerous"
That cancer is malignant by definition is extremely well known. I won't respond further.
P.S. I looked through your other comments and can highly recommend you to https://www.reddit.com/r/confidentlyincorrect/