Desmoid fibromatosis of the pelvis originating from a J-pouch of small bowel (case report)

This clinical case presents a successful treatment experience in a young patient with a large desmoid tumor and familial adenomatous polyposis syndrome, previously operated on for rectal cancer with proctocolectomy.

OBJECTIVE: to analyze the epidemiology and pathophysiology of the disease and evaluate the tactics of working with this pathology, we reviewed the global medical literature, the patient's anamnestic data, the results of diagnostics and intraoperative decisions, and the results of histological examination of the surgical specimen.

PATIENTS AND METHODS: patient K., 28, presented as part of the dynamic monitoring of her primary oncological disease in February 2022. Rectal cancer at 5 cm cT2N0M0 (urTisN0M0), ARS syndrome, histologically — intestinaltype adenocarcinoma and abdominal discomfort not relieved by analgesics. In April 2022, she underwent chemoradiation therapy with preliminary ovarian transposition, followed by a proctocolectomy with the creation of a pelvic small bowel pouch. In March 2024, she became pregnant naturally, delivering a healthy baby via cesarean section. In April 2025, during oncology monitoring, a 6 cm diameter pelvic mass was detected, which, according to CT and MRI, reached 13.5 cm in diameter four months later. An ultrasound-guided puncture was performed for histological confirmation, and the diagnosis was desmoid fibromatosis. A consultation was held, and the decision was made to remove the desmoid tumor and perform an obstructive resection of the pouch.

RESULTS: an analysis of the literature on the practical aspects of treating this pathology was conducted, highlighting the need to develop standardized clinical guidelines for the prevention, diagnosis, and treatment of intra-abdominal desmoids due to the unpredictable course of this disease and the lack of clearly established patient management concepts.

CONCLUSION: this clinical case is notable for its rare occurrence of a desmoid tumor, poorly studied in the medical community, which arose in a young patient diagnosed with familial adenomatous polyposis and the fact of a spontaneous pregnancy following pelvic radiation therapy and extensive surgical intervention.

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