[A case of abdominal desmoid tumor that was difficult to differentiate from urachal tumor].

A 76-year-old male patient complained of frequent urination. Computed tomographic and magnetic resonance imaging scans revealed a heterogeneous mass involving his bladder, prostate and Sigmoid colon. He was diagnosed with an invasive urachal tumor and surgery was performed due to severe tumor adhesion to adjacent organs. Partial resection of the tumor was performed with partial cystectomy and sigmoidectomy. A post-operative pathological diagnosis revealed the tumor was a desmoid abdominal wall tumor. The desmoid abdominal wall tumor was not easily differentiated preoperatively from an urachal tumor.