Consistent with the increased vascularization (Figure 1E), the vascular density of tumor lymph nodes was higher in Ibtk+/-Eμ-myc than Ibtk+/+Eμ-myc mice, as shown by immunofluorescence staining of the blood vessel specific marker CD31 (Figure 2A,B). The gene discussed is PECAM1; the disease is neoplasm.