New intra-abdominal mass after operation for colorectal cancer: desmoid tumor versus peritoneal seeding.

PURPOSE: To identify differential clinical and imaging findings between intra-abdominal desmoid tumors and peritoneal seeding that developed after surgery for colorectal cancer.

METHODS: 8 patients (9 desmoid tumors) and 11 patients (13 peritoneal seeding masses) were enrolled in our retrospective study. Patients with three or more tumors were excluded. Clinical findings including location of initial tumors, type of surgery, T- and N-stages of initial tumors, time interval between initial surgery and development of intra-abdominal tumors, and level of carcinoembryonic antigen (CEA) were evaluated. Imaging findings of intra-abdominal tumors including size, number, growth rate, location, shape, homogeneity, relative enhancement, and maximum standardized uptake value were evaluated. The Mann-Whitney U test and Fisher's exact test were used to compare clinical and imaging findings between desmoid tumors and peritoneal seeding.

RESULTS: In patients with a desmoid tumor, initial T-stage, initial N-stage, and level of CEA at the time of surgery for intra-abdominal tumor were lower than in patients with peritoneal seeding (p = 0.027, p = 0.033, and p = 0.017). The desmoid tumors were frequently located in the small bowel mesentery (p = 0.018) and were larger at detection (p = 0.041). Round or ovoid shapes on CT images were more frequently observed with the desmoid tumors (p = 0.035).

CONCLUSIONS: Stage of colorectal cancer, CEA level, and location, size, and shape of new intra-abdominal tumors can be helpful for differentiating between intra-abdominal desmoid tumors and peritoneal seeding in patients with a history of colorectal cancer surgery.