A Rare Case Desmoid Tumour of Appendix Mimicking a Gastrointestinal Stromal Tumor

A 48 year-old male patient with complaint of an abdominal pain and a palpable abdominal mass came to our general surgery outpatient clinic. The computed tomography revealed a well-circumscribed solid mass, approximately 12 cm in diameter, which is thought to be a gastrointestinal stromal tumor originating from the cecum. The colonoscopy detected an external pressure on the cecum. No remarkable feature was noted in the patient?s history. Right hemicolectomy was performed. Pathological examination revealed a collagen-rich hypocellular mesenchymal tumor originating from the appendiceal wall, which was negatively stained with CD117 immunohistochemical antibodies. The histopathological diagnosis revealed a desmoid tumor (fibromatous lesions). The patient was discharged on postoperative day 6 and was transferred to the oncology department.