Histology and immunohistochemistry (IHC) analysis showed that B220+ B cell lymphomas accounted for over 87% of tumors examined, and occurred in all three genotypes: 4/14 FIH+/+, 10/21 FIH+/Δ1-2 and 14/22 FIHΔ1-2/Δ1-2 mice (Fig. 1C and SI Appendix, Fig. S1D). The gene discussed is PTPRC; the disease is B-cell non-Hodgkin lymphoma.