Treatment of Orbital Desmoid-type Fibromatosis With Sorafenib

Desmoid-type fibromatosis is a rare tumor, particularly in the orbit, with fewer than 10 cases of primary orbital desmoid-type fibromatosis reported in the literature. The authors present a case of an infant who presented with rapid onset of OD proptosis, disc edema, and hyperopic shift who was found to have a retrobulbar desmoid-type fibromatosis. After initial biopsy, due to risk of vision loss with complete excision, the tumor was treated with sorafenib, a tyrosine kinase inhibitor. During the course of treatment with sorafenib, the tumor stabilized and then regressed in size. To the authors’ knowledge, this is the first reported case of orbital desmoid-type fibromatosis to be treated with sorafenib.

Desmoid fibromatosis (DF) is a rare locally aggressive, connective tissue malignancy developing in musculoaponeurotic tissues with an incidence of 2-4 per million population. We presented a case of a 3-year-old patient with a left parapharyngeal mass, histopathological examination suggesting DF, who underwent complete surgical excision without recurrence or requirement of cardiac resynchronization therapy.

A 27-year-old woman was confirmed to have extraabdominal desmoid-type fibromatosis. Desmoid-type fibromatosis is a very rare connective tissue neoplasm with the extraabdominal type even more rare. It is most commonly found in proximal structures such as shoulders, neck, chest, and extremities. There are few case reports for desmoid-type fibromatosis located in paraspinal soft tissue. We report a case of desmoid-type fibromatosis mimicking a myxofibrosarcoma. Teaching Point: Even if there are suggestive findings for malignant soft tissue tumor on radiologic evaluation, histological confirmation is necessary before surgical treatment.

Introduction: While activation of beta-catenin is associated with desmoid fibromatosis (DF), mechanisms by which this oncogene initiates tumorigenesis are unclear as are factors underlying variable biologic behavior in the disease and vulnerability to targeted therapies. This study sought to define downstream pathways dysregulated by beta-catenin that may be modulated to potentially affect patient outcome. Methods: Multiple primary DF cell lines were developed from surgical specimens, validated by Sanger sequencing, and immortalized by ectopic expression of TERT. Gene expression was assessed in DF tumors (n=45) with U133A arrays and by RNA-seq in cells. Direct targets of beta-catenin were identified by CHIP-seq. Lentiviral systems were used to deliver shRNA (or scramble control) and overexpression constructs. Cell proliferation, protein levels/phosphorylation and gene expression were assessed by CyQuant DNA quantification, immunoblot, and RT-PCR, respectively. Endothelial cell (HUVEC) tube formation was quantitated using light microscopy. Results: Gene set enrichment analysis performed on RNA-seq data comparing DF cells treated with shRNA directed against CTNNB1 showed downregulation of hypoxia-regulated genes, and unsupervised analysis clustered 45 DF tumors separately from normal mesenchymal tissue based on the expression levels of these genes. CTNNB1 knockdown (KD) was associated with reduction in HIF1A and ability of DF cells to induced endothelial tube formation in HUVEC co-cultures (71%, p<0.001); ectopic expression of HIF1A in CTNNB1 KDs rescued this effect. HIF1A KD itself inhibited DF induction of HUVEC tube formation (49%, p<0.001), but did not affect DF cell proliferation. CHIP-seq nominated ABL1, a known regulator of HIF1 translation, as a direct target of beta-catenin. CTNNB1 KD caused 65% (p=0.01) decrease in ABL1 expression, and reduction in levels of c-ABL, its downstream target p-CRKL, and HIF1-alpha. Unlike HIF1A, ABL1 KD also reduced proliferation in multiple DF cell lines (up to 90%) as did direct inhibition of c-ABL with its inhibitor dasatinib (IC50 <50nM). Dasatinib and sorafenib, a PDGFR-beta inhibitor of clinical benefit in DF, both reduced cellular levels of p-ABL, p-CRKL and HIF1a expression in DF cells. Sorafenib also inhibited HUVEC tube-formation (59% at 1uM, p<0.05) induced by DF. Conversely, exogenous PDGF-BB stimulated DF proliferation (53% increase at 20ng/ml, p<0.05), increased p-ABL, p-CRKL and HIF1a in DF and promoted endothelial cell tube formation (2-fold, p<0.05) when added to DF and HUVEC co-cultures but not HUVEC cell cultures alone. Conclusion: ABL1 is a transcriptional target of beta-catenin in DF cells and is necessary for proliferation and maintenance of HIF1-alpha levels. Regulation of c-ABL activity by PDGFR-beta and targeted therapies modulates DF cell proliferation and paracrine signaling, suggesting a reason for variable biologic behavior between tumors and a mechanism for sorafenib activity in DF. This finding may point to markers predictive of outcome in patients.

Desmoid tumors are rare benign myofibroblastic neoplasms that do not have metastatic potential. In this study, we report a case of a desmoid tumor in the left rectus abdominis muscle of a female patient. Computed tomography, abdominal ultrasound and magnetic resonance imaging were obtained preoperatively. We performed a complete resection with negative margins. Microscopic evaluation revealed a desmoid tumor. To definitively diagnose abdominal wall masses, imaging modalities must be used in conjunction with clinical history and histologic findings. For these masses, surgical resection is the preferred line of treatment.

Desmoid-type fibromatosis (DTF) is a rare benign lesion that usually arises from the abdominal wall or extremities and rarely from the mesentery or intrabdominal organs. Malignant peritoneal mesothelioma is also a rare, yet aggressive disease. To our knowledge, this is the first case report of desmoid-type fibromatosis in the setting of malignant peritoneal mesothelioma. Case presentation: An early 30-year-old female was referred to our center for large intra-abdominal mass concerning for recurrent malignant peritoneal mesothelioma after previous cytoreductive surgery with hyperthermic intraperitoneal chemotherapy and adjuvant chemotherapy. Further investigation revealed a large mesenteric mass, which was resected en bloc with the cecum and terminal ileum. Pathologic findings confirmed a surprising diagnosis of desmoid-type fibromatosis. Conclusions: No adjuvant therapy was offered to this patient due to negative tumor margins; however, close follow-up will be provided for recurrence of both malignant peritoneal mesothelioma and desmoid-type fibromatosis, which can be differentiated in the future via biopsy in this patient.