When the Fhit knockout mouse model was first developed and characterized, there were two noteworthy but unexplained features early in the study and another that was noted while tallying spontaneous tumors in mice between 1 and 2 years of age: first it was clear that carcinogen treatment induced many-fold more upper gastrointestinal tumors in Fhit-/- than in WT mice; secondly, some Fhit-/- mice on the mixed 129XB6 background spontaneously developed Muir-Torre-like sebaceous tumors [11], that had formerly been known to occur in mismatch repair-deficient cancers. The gene discussed is FHIT; the disease is digestive system neoplasm.