Differentiation of intra-abdominal desmoid tumor from peritoneal seeding based on CT and/or ¹⁸F-FDG PET-CT in patients with history of cancer surgery

Purpose

To investigate differential imaging features of intra-abdominal desmoid tumors and peritoneal seeding in patients with history of cancer surgery.

Methods

Thirty-two patients who had a single pathologically proven intra-peritoneal lesion that developed after cancer surgery were enrolled between January 2000 and June 2019. There were 16 desmoid tumors and 16 peritoneal seeding lesions. Portal phase CT and/or ¹⁸F-FDG PET findings were analyzed by two radiologists in consensus for the following items: location, size, shape, margin, contour, homogeneity, necrosis, adjacent organ invasion, calcification, intra-lesional fat, peritoneal infiltration, mass effect, and degree of enhancement. Hounsfield units (HU) and maximum standardized uptake values (SUV_max) of the lesions were measured. Imaging findings were compared using the Chi square test, Fisher's exact test, and student t test.

Results

Desmoid tumors frequently showed well-defined margins (9/16) and smooth contours (12/16), whereas peritoneal seeding had ill-defined margins (13/16) and lobulated contours (11/16) (P = 0.028 and 0.013, respectively). Intra-lesional fat was found more frequently in desmoid tumors (7/16) than peritoneal seeding (1/16) (P = 0.014). Desmoid tumors showed iso-attenuation (13/16) compared to psoas muscle in portal phase, while peritoneal seeding depicted high attenuation (12/16) (P = 0.002). Mean HU was significantly lower in desmoid tumors (64.3) than peritoneal seeding lesions (95.1) (P = 0.001). However, the mean SUV_max of desmoid tumors (4.1) did not significantly differ from peritoneal seeding lesions (5.2) (P = 0.519).

Conclusion

Several CT features including iso-attenuation in portal phase and presence of intra-lesional fat can be helpful in differentiating desmoid tumors from peritoneal seeding in patients with history of intra-abdominal cancer surgery.