Abstract:Objective To investigate the CT and MRI signs of abdominal wall type desmoid fibromatosis and analyze its pathological basis, so as to improve the imaging diagnosis of this disease. Methods The clinical data of 5 patients with abdominal wall desmoid-type fibromatosis confirmed by surgery and pathology in Nanjing Jiangbei Hospital from September 2018 to April 2021 were collected. Among them, 3 cases received plain CT and contrast-enhanced CT, and 2 cases received plain CT and MRI. CT and MRI imaging features were analyzed retrospectively. Results All 5 cases were single lesion. The lesions were located in the right rectus abdominis in 4 cases and the left internal oblique abdominis in 1 case. Four of them had a history of abdominal wall injury in recent 2 years. Plain CT showed that the lesion was lower than the soft tissue density shadow of the same layer of muscle, with the spindle shape and uniform density, the long axis was consistent with the direction of muscle fibers, and there was no calcification and cystic change. The contrast-enhanced CT showed a “slow in and slow out” mode. MRI showed slightly low signal on T₁WI. On T₂WI, the signal was slightly high and high, respectively. In 1 case, the signal was uneven, with banded low signal, which was a low signal area formed by dense collagen fibers. DWI was a high signal and ADC was a little low signal. In 1 case, the boundary of the lesion was unclear, and the fascial tail sig" was visible. In 1 case, the lesion was “claw” like infiltration and growth. In the histopathology, the tumor was mainly composed of proliferative spindle fibroblasts and collagen fiber bundles. The blood vessels in the stroma were small and narrow, and mitotic images were rare. Immunohistochemical markers β-Catenin and Vimentin were positive. Conclusion Abdominal wall desmoid-type fibromatosis has certain characteristic signs on CT and MRI. Compared with CT, MRI has more advantages in tumor components and infiltration of surrounding tissues.