Feng-Chun Yang’s team, studying neurofibromas, discovered that mast cells in the ECM can infiltrate neurofibromas and secrete proteins that reshape the ECM and initiate vascularization, establishing a new interaction between Nf1−/− (homozygous mutation of the Nf1 tumor suppressor gene) SCs and Nf1+/− (heterozygous mutation of the Nf1 tumor suppressor gene) mast cells. The gene discussed is NF1; the disease is plexiform neurofibroma.