[_qua]

Some infections cause cancer-like growths or masses though they're not actually cancer. Though off the top of my head none that I would suspect would survive a trip through stomach acid.

[M95D]

You can get HPV directly from the mouth. It doesn't need to get to the stomach. It causes papillomas to appear, which can look like tumors.

Same for herpes virus. It causes ulcerations, but too common and small to be confused with cancer.