A single dominant susceptible gene determines spontaneous development of thymoma in BUF/Mna rat.

Rats of the BUF/Mna strain developed spontaneous epithelial thymomas morphologically indistinguishable from human homologues at virtually 100% incidence. Segregation of thymoma development among crosses between BUF/Mna and ACI/NMs, which has 0% thymoma incidence, indicated that thymoma susceptibility was determined principally by a single autosomal dominant gene Tbm-1 (thymoma in BUF/Mna rats). In these crosses, another autosomal dominant or semidominant gene(s) contributed by ACI/NMs parents moderately reduced the thymoma incidence.