Retroperitoneal desmoid-type fibromatosis: Challenges in the preoperative diagnosis and treatment

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Desmoid tumors (DT) are rare fibroblastic, soft-tissue tumors that do not metastasize but can aggressively infiltrate tissues causing significant chronic discomfort and/or functional impairment. In the pediatric population, the incidence of DT is greatest during infancy and adolescence but can occur at any age. Dysregulated ?-catenin, most commonly resulting from mutations in either CTNNB1 or germline APC (adenomatous polyposis coli) drives DT. Most cases are sporadic but some are associated with predisposition syndromes such as familial adenomatous polyposis (FAP). Historically, treatment has been surgery. However, the recurrence rate after surgery can be high. Various systemic cytotoxic chemotherapy regimens used in other soft-tissue sarcomas have been applied to DT with differing results. Given the chronic and rarely life-threatening nature of this disease and the potential short- and long-term toxicity of these regimens, especially in children, alternative non-cytotoxic interventions have been investigated. Molecularly targeted agents such as tyrosine kinase and gamma secretase inhibitors have shown activity against DT. Innovative local control therapies are being employed as alternatives to surgery and radiation. Periods of prolonged stability and spontaneous regression in the absence of therapy in some patients has prompted wider adoption of an upfront active surveillance approach in the appropriate setting. This review will briefly summarize the epidemiology, pathophysiology, and clinical presentation of DT in children, then focus on historical, current, and future pharmacotherapeutic management and finally, propose areas for future study.

Purpose: This prospective nationwide cohort study aimed to investigate desmoid-type fibromatosis (DF) outcomes, focusing on the prognostic value of CTNNB1 mutations. Experimental design: ALTITUDES (NCT02867033) was a nationwide prospective cohort study of DF diagnosed between January 2016 and December 2020. At diagnosis, CTNNB1 molecular alterations were identified using next-generation sequencing or Sanger sequencing. The primary endpoint was event-free survival (EFS) (progression, relapse, or death). We enrolled 628 patients managed by active surveillance (AS), surgical resection (SR), or systemic treatment as front-line therapy. Results: Overall, 516 (82.2%) patients (368 females [71.3%], median age 40.3 years [range, 1-89]) were eligible for analysis. In 435 (84.3%) cases, there was one CTNNB1 molecular alteration: p.T41A, p.S45F, or p.S45P. The front-line management was AS in 352 (68.2%), SR in 120 (23.3%), and systemic treatments in 44 (8.5%) patients. CTNNB1 mutation distribution was similar across the three therapeutic groups. The median follow-up period was 24.7 (range, 0.4-59.7) months. The estimated 3-year EFS rate was 66.2% (95%CI, 60.5%-71.2%). DF harboring p.S45F was significantly associated with male sex (p=0.03), non-abdominal wall sites (p=0.05), pain (p=0.007), and large tumor size (p=0.025). CTNNB1 p.S45F mutation was not significantly associated with EFS, either in univariate (hazard ratio [HR]=1.06; 95% confidence interval [CI], 0.65-1.73; p=0.81), or in multivariate analysis (HR=0.91; 95% CI, 0.55-1.49; p=0.71). Conclusions: We found that CTNNB1 mutation profile was associated with unfavorable prognostic factors but was not a prognostic factor for EFS.

Purpose: To prospectively assess the behaviour of primary sporadic (not FAP associated) desmoid fibromatosis (DF) managed by active surveillance (AS). Experimental design: This is an Italian prospective, multicenter, observational study (NCT02547831) including patients {greater than or equal to}16 years with primary sporadic DF at any site. Patients were assessed by Response Evaluation Criteria in Solid Tumor (RECIST) version 1.1 . Primary end-point was progression-free survival (PFS) at 3 years. Treatment-free survival (TFS) was also analyzed. PFS and TFS were calculated by Kaplan-Meier plots and compared by log-rank test Cox proportional-hazard multivariable regression analyses were performed. Results: From 2013 to 2018 108 consecutive patients were included (82% female); median age was 39-yr; median size was 51 mm. CTNNB1 mutations were: T41A (50%); S45F (12%); other (19%); WT (19%). At 32.3-month median-FU, 42/108 (39%) showed RECIST progression. Spontaneous regression (SR) was initially observed in 27/108 (25%), while it followed dimensional progression in other 33/108 (31%). PFS at 36 months was 54.5% (95% CI, 44.9%-66.1%). Thirty-five/108 (32%) patients received active treatments, 18/108 (17%) after RECIST progression and 17/108 (15%) after symptomatic progression. TFS at 36 months was 65.9% (95% CI, 57.3%-75.9%). Larger tumor size and extremity location were associated to shorter TFS and a trend for S45F mutation was also observed (p=0.06), while none of the above variables was significantly associated to PFS. Conclusions: In primary DF, AS can be proposed, since disease stabilization and SR frequently occur. However extra care should be taken for patients with tumors of larger size, extremity location and S45F mutation.

A 17-year-old boy with lower abdominal pain was diagnosed with a gastrointestinal stromal tumor (GIST) or a hematoma at a local hospital. He had no history of FAP, trauma, or previous surgery. Operative findings revealed that the tumor was a hard mass firmly attached to both the greater curvature of the stomach and the inferior pole of the spleen. Pathologically, the tumor was diagnosed as a desmoid tumor derived from the stomach.

Background: Fibromatosis is a group of benign tumors originating from connective tissues of muscle, overlying fascia, periosteum, or aponeurosis. However, they might need several excisional resections, owing to compressive effects on adjacent vital structures. Case Report: Here, we discussed a case of submandibular fibromatosis in a 3-year-old girl. She underwent a conservative surgical procedure without a wide mandible bone resection. She received no adjuvant therapy. The postoperative period was uneventful with an appropriate cosmetic and functional outcome. A 1-year follow-up revealed no recurrence. Conclusion: Fibromatosis of the head and neck in children is a rare condition, which needs a multidisciplinary agreement for its appropriate management. A complete surgical removal often leads to a proper outcome. Adjuvant therapy should also be kept in mind for recurrent lesions not candidate for surgical removal or in case of remnant tumors.