Asymptomatic Mesenteric Desmoid Fibromatosis: A Diagnostic and Therapeutic Challenge

Summary

Background: Desmoid fibromatoses are rare, benign neoplasms of myofibroblast origin that lack metastatic potential but can be locally invasive. Diagnosis and management are challenging as these are based on a multitude of factors such as symptomatology, tumor location, risk of recurrence, and the possibility of treatment-induced morbidity. Case Presentation: A healthy 48-year-old Filipino woman presents with an 2x3 cm incidental jejunal mesenteric mass found intraoperatively during the excision of her choledochal cyst. Histopathology of the core-needle biopsy revealed desmoid fibromatosis. An initial watchful waiting approach was employed since the patient was asymptomatic and resection would cause significant bowel loss. After three months, her abdominal CT scan shows that the mass had progressed, to 4.7 x 4.5 x 4.7cm. Anti-hormonal therapy with high-dose Tamoxifen (120mg daily) was initiated due to its limited toxicity and low cost. The patient is currently asymptomatic, on her sixth month of treatment. The tumor remained stable at 4.5 x 4.6 x 4.7cm, on repeat abdominal imaging. Conclusions: Desmoid fibromatosis represents a benign histology with a malignant and unpredictable course. It warrants a multidisciplinary team approach upfront. Watchful waiting is an appropriate first line option, especially in asymptomatic tumors and those found in non-critical locations. In case of progression, management should be site specific and via a stepwise approach. Therapeutic toxicities, such as significant intestinal loss upon resection, should be carefully weighed before choosing treatment. Preferred management for patients with intra-abdominal desmoid tumors that progress after observation has shifted towards non-surgical approaches or systemic therapies, including antiestrogens, NSAIDs, tyrosine-kinase inhibitors (sorafenib, pazopanib and imatinib) and chemotherapy (methotrexate and vinblastine, and vinorelbine). A stepwise escalation of therapy from less to more toxic agents are a reasonable approach. It is also possible to discontinue treatment and resume watchful waiting for patients not progressing for two years