Gastrointestinal tumors are a moderately rare occurrence in NF1 patients, but the underlying biology of these tumors has not been well understood making it difficult to figure out how they can be best managed clinically. Now with a new publication* researchers at the University of Texas Southwestern Medical Center have a better handle on this and furthermore have generated a genetically-engineered mouse model that develops gastro intestinal stromal tumors due to Nf1 gene deficiency in GI tract fibroblasts. This is associated with hyperactivation of the cell signaling pathway ERK in the gastric epithelium. The mice should provide a useful model to study the biology of the GI tumors that might affect NF1 patients and to test drug therapies to treat these. *Mice Lacking Neurofibromin Develop Gastric Hyperplasia (2009) Lu Lin, Jian Chen, James A. Richardson and Luis F. Parada. Am. J. Physiol. Gastrointest. Liver Physiol. Aug 6. [Epub ahead of print]