Mesenteric fibromatosis presenting as fever of unknown origin.

We report a case of fibromatosis, soft tissue tumors that are benign histologically, but exhibit behavior intermediate between benign and malignant diseases. Mesenteric fibromatosis grows vigorously without a general inflammatory reaction, and its symptoms are the result of obstruction and/or compression of the intestine. However, in our case, the general inflammatory reactions of fever and C-reactive protein (CRP) elevation was present at an early stage. Because this inflammatory reaction disappeared after surgical resection, it may have been induced by some inflammatory factors produced in the tumor, such as those produced in inflammatory fibrous histiocytoma. We found that computed tomography was useful in the detection of the cause of fever of unknown origin, and suggest that it should be recommended in cases of long-lasting unexplainable fever.