Objective  To investigate the ¹⁸F-fluorodexyglucose (FDG) PET/CT imaging characteristics of aggressive fibromatosis (AF).

Methods  A retrospective analysis was conducted on the clinical data and ¹⁸F-FDG PET/CT images of 14 patients (5 males, 9 females; aged (45.0±14.8) years) with histopathologically confirmed AF admitted to the Affiliated Qingdao Central Hospital of Qingdao University from October 2010 to December 2021. The location, size, shape, density, boundary and surrounding invasion, distant metastasis, maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the lesions were measured and recorded. Spearman correlation analysis was used to evaluate the correlation of SUV_max, MTV, and TLG with the maximum diameter.

Results  The location of all the lesions could be divided into right lower abdominal wall (five cases) and extra-abdominal wall (nine cases), including four cases in the dorsal shoulder, three cases in the right chest wall, one case in the right thigh, and one case in the right subcutaneous axilla. The maximum diameter of the lesions was (3.5±2.7) cm with a range of 1.0–8.2 cm. The morphology of all the lesions could be classified as round-like (three cases), pyknotic (nine cases), and irregularly infiltrated (two cases). The density of all the lesions was divided into homogeneous (12 cases) and inhomogeneous with cysts (two cases). The boundaries of all the lesions were divided into clearly delineated (12 cases) and indistinctly delineated (two cases). For the two cases with indistinct boundaries, one had indistinct delineation of the ipsilateral erector spinae muscle and involvement of the contralateral erector spinae muscle. The other exhibited invasion of the local scapula, causing the thickening of the corresponding bone cortex. All the patients had no distant metastasis. The SUV_max, MTV, and TLG of all the lesions were 3.96 (2.91, 12.82), 2.10 (1.46, 29.55) cm³, and 19.10 (2.91, 79.04) g, respectively. No correlation was found between SUV_max and the maximum diameter (r=−0.018, P>0.05). MTV and TLG were positively correlated with the maximum diameter (r values: 0.901, 0.847, both P<0.01). Among the 14 lesions on PET/CT imaging, 11 were superficial lesions (lesions of muscle, fascia, or aponeurosis area that are adjacent to the subcutaneous fat layer); their ¹⁸F-FDG metabolism was slightly increased, and their SUV_max were 3.40 (2.90, 4.20). Three cases were deep lesions (lesions of muscle, fascia, or aponeurosis area that are not adjacent to the subcutaneous fat layer); their ¹⁸F-FDG metabolism was significantly increased, and their SUV_max were 12.82, 13.50, and 11.50.

Conclusions  AF has certain ¹⁸F-FDG PET/CT imaging characteristics. When the lesion is located in the superficial part, the density and the metabolism of ¹⁸F-FDG is low. When the lesion is located in the deep part, the metabolism of ¹⁸F-FDG is significantly increased. Therefore, ¹⁸F-FDG PET/CT imaging is of great value in the diagnosis, judgement of the relationship with adjacent structures, and staging of AF.