TP53 and lymphoma: It is worth noting that while p53 protein is absent from the entire B cell population in p53rev/rev mice, the lymphomas that develop in these mice bear the unique histopathologic features of SMZL and are thus quite distinct from the B lymphomas recently reported to occur in B cell-specific p53 knockout mice [33]; in that strain, p53-deficient B lineage cells were generated by the activity of mb1-Cre on a floxed p53 allele.