Abstract
Desmoid-type fibromatosis (DF) is a rare soft tissue lesion with an annual incidence of 2 to 4 per million population and peak incidence occurring at approximately 4.5 years of age. While benign, the tumor has a locally aggressive infiltrative growth pattern and a high rate of recurrence. Given the functional and aesthetic implications of excision and reconstruction in the facial skeleton, novel medical treatment options are highly desirable. We describe the case of a 3-year-old boy who presented with an enlarging, asymptomatic mass involving the left mandible. Biopsy revealed an immunohistochemical profile consistent with DF. Despite the high likelihood of recurrence, conservative, mandible-sparing en bloc resection and limited mandibulectomy were performed. Pathological and immunohistochemical analysis of the resection specimen revealed DF with grossly positive margins and elevated expression of angiotensin II type 1 receptor. Postoperative medical treatment with the angiotensin receptor blocker losartan was initiated. The patient remains medically stable and disease progression-free on repeat imaging at 20 months post-resection. We describe for the first time the successful use of the angiotensin blocker losartan following conservative surgery for management of DF.