Mesenteric fibromatosis mimicking a gastrointestinal stromal tumor

Mesenteric fibromatosis is a locally aggressive tumor of the mesentery with a high propensity for bowel involvement. Mesenteric fibromatosis often mimics gastrointestinal stromal tumors in size, location and immunohistochemical features. We report the case of a 30-year-old male who underwent resection of a mesenteric tumor, initially diagnosed as gastrointestinal stromal tumor. The tumor was categorized as high-risk and the patient was treated with chemotherapy. Two years later the patient was found to have a mass in the mesentery and restarted on chemotherapy. The tumor did not respond to medical management. The patient underwent a second en bloc resection and pathology results were conclusive for mesenteric fibromatosis. This case highlights the significance of accurately differentiating mesenteric fibromatosis from gastrointestinal stromal tumor. Making a concrete diagnosis is often difficult because both gastrointestinal stromal tumors and mesenteric fibromatosis share a number of morphological and immunohistochemical features including CKIT expression.