Abstract
A desmoid tumor is a fibroblastic proliferation of mesenchymal origin, which has no metastasizing potential but is locally aggressive. Although treatment has shifted to observation and active surveillance for newly diagnosed patients with desmoid tumors, intra-abdominal mesenteric tumors or tumors that persistently grow and provoke symptoms may need prompt surgical treatment. There have only been a small number of case reports that illustrate large sporadic intra-abdominal mesentery-deriving desmoid tumors in which the longest diameter was ≥19 cm. In the present study, an adolescent male patient with a rapidly growing 38-cm long sporadic intra-abdominal desmoid tumor of mesenchymal origin is reported. The patient was treated with chemotherapy followed by surgical resection due to non-responsiveness and progression of symptoms, then with maintenance adjuvant chemotherapy to prevent recurrence due to the large size of the tumor. Despite the rapid growth of the tumor and its high occupancy in the intra-abdominal cavity, an R0 resection was successful with organ preservation. The patient has been recurrence-free for 2 years, and further follow-up is expected in the future.