Remarkably, while suppressing neurofibromas, genetic deficiency of NF-κB1 promotes immortalization of Tax-expressing macrophages and causes massive infiltration of neoplastic macrophages into the spleen, lymph nodes and adrenal glands, resulting in splenomegaly, lymphadenopathy and adrenomegaly in mice. Here, NFKB1 is linked to plexiform neurofibroma.