Gavra, ????? ????? ?, ?.
http://hebrewbooks.org/pdfpager.aspx?req=14334&st=&pgnum=40&hilite=
Are ulcers listed in the ???????
Thank you.
The Chazon Ish basically gives two possibilities. The first is that the Chachomim were Koveah Treifos based on what they could do medically at the time. Had they lived now, they would not have included it in the Treifos. None the less, the Halachah is set by what the Chachomim decided then (interestingly, another proponent of this Shittah is Rabbi Nathan Slifkin).
The second is evolution, and that the Refuos would not have worked on the bodies of people during the time of Chazal, but they can work on ours.
A hole in the stomach is listed as a Treifah by the Rambam; I can’t speak to “The Braisah”. But if you would like, you can switch the example to an amputee above the knee, which we know can live a long life now but still has the “din” of a Treifah.