GH – If in fact there is a source in the Gemara as others have stated, then your post is highly problematic and inappropriate.
Even if there isn’t, I think that it is still unnecessarily negative. If you would prefer to call it “cancer” then call it cancer, but don’t attack those who use a different term than you do. That strikes me as close-minded especially if you haven’t asked them why they use this term. Maybe there is a good reason for it.
And there is no reason to assume that calling it “The machla” instead of cancer has any connection to how open people are about it. You can call it “The Machla” and be open about it and you can call it cancer and be closed about it.