Abstract
BACKGROUND: Aggressive fibromatosis (AF), also known as desmoid tumor or desmoid-type fibromatosis, is a rare soft tissue neoplasm that can occur in almost any part of the body. Although it is a benign disease, AF is aggressive and infiltrative and has a high recurrence rate after surgery. Common sites for intra-abdominal AF are the small bowel mesentery, retroperitoneum, and pelvis. AF in the colon is extremely rare. CASE SUMMARY: Here, we report the first case of sigmoid colon AF, which was accidentally discovered in a 27-year-old woman during laparoscopic myomectomy. Computed tomography confirmed a slightly enhanced mass in the sigmoid colon. Subsequent colonoscopy did not reveal a mass in the colonic lumen, but a suspected external compress was found in the sigmoid colon. Surgical disease involving a gastrointestinal stromal tumor was suspected. The patient underwent laparoscopic exploration, and sigmoidectomy with a negative margin was performed to excise the mass. Postoperative immunohistochemistry revealed that the mass was an AF. The patient recovered well and was recurrence-free at the 30-month follow-up without adjuvant therapy. CONCLUSION: AF should be considered in the differential diagnosis of subepithelial colon masses. Radical resection alone can achieve good outcomes.