Gardner's syndrome is an autosomal dominant inherited disorder. Familial polyposis of the colon, osteomas, hypertrophy of the retinal-pigmented layer and a multitude of soft tissue tumors are characteristic features. The syndrome may be presented with colonic or extracolonic symptoms. A 75-year-old male patient presented to Al-zahra Clinic with diffuse abdominal pain. An abdominal surgery was performed on him due to invasive abdominal mass. The surgical specimen was examined by H&E and immunohistochemical staining. The final diagnosis was fibromatosis. There was a history of gardner’s syndrome in his family. Colonoscopy was done to confirm the diagnosis of gardner’s syndrome. The diagnosis of gardner’s syndrome was made according to following findings: abdominal fibromatosis, multiple jaw osteomas and polyposis coli. The patient with gardner’s syndrome can present with abdominal fibromatosis even in an old age. In IHC staining CD117 was seen with coarse granular cytoplasmic pattern in fibromatosis, and so, this pattern of CD117 staining can be a clue to the diagnosis of fibromatosis.