Higher magnification showing cytologically bland spindle cells with vesicular nuclei, punctate nucleoli and indistinct cytoplasmic borders. Scattered mast cells are present. The differential diagnosis of mesenteric fibromatosis includes other fibrosing conditions seen in this location such as idiopathic retroperitoneal fibrosis, inflammatory myofibroblastic tumor, and sclerosing mesenteritis (mesenteric panniculitis). Mesenteric fibromatosis is usually negative for KIT (CD117); however, some labs. have reported positivity for this marker (due to antibody quality or suboptimal technique) resulting in confusion with gastrointestinal stromal tumor. Beta-catenin and DOG1 can help distinguish between the two. Mesenteric fibromatosis is beta-catenin positive (nuclear staining) and DOG1 negative; mesenteric GIST would be beta-catenin negative and DOG1 positive.