Objective  This study aimed to explore the differences in clinicopathological characteristics and recurrence risk between patients with intra-abdominal desmoid-type fibromatosis (DTF) located in the peritoneal cavity and those with retroperitoneal anatomical locations, and to evaluatethe impact of margin status on recurrence prediction.

Methods  We retrospectively analyzed 31 patients diagnosed with intra-abdominal DTF who underwent surgical resection at the Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College between March 2014 and March 2024. Patients were assigned into retroperitoneal and intra-abdominal groups based on the anatomical location of the tumor, and their clinical data were collected and statistically analyzed. The Kaplan-Meier method was used to assess recurrence-free survival (RFS), and multivariate analysis was performed using a Cox proportional hazardsmodel.

Results Tumor diameter in the retroperitoneal group was significantly smaller than that in the intra-abdominal group (7.08±2.20) cm vs. (8.14±5.57) cm, P=0.036, and both the surgical time and amount of bleeding were significantly increased (P<0.05). The intra-abdominal group had significantly longer RFS than the retroperitoneal group (76.56±7.19) months vs. (49.62±12.37) months, P=0.045. Cox proportional hazards model analysis indicated that the recurrence risk for retroperitoneal tumor patients was 5.98-fold that of patients from the intra-abdominal group (hazard ratio HR=5.98, 95% confidence interval CI: 1.12–31.92, P=0.037), and the recurrence risk for patients with positive margins (R1) increased 14.7-fold (HR=14.7, 95% CI: 1.42–99.9, P=0.024).

Conclusions The risk of recurrence of retroperitoneal DTF is significantly higher than that of intra-abdominal DTF, and positive surgical margins (R1 resection) are an even stronger factor that lead to a markedly increased risk of recurrence.