Desmoid fibromatosis in a child with DICER1-related tumor predisposition.

Background. Desmoid fibromatosis (DF) is a rare mesenchymal tumor with invasive growth, a high relapse rate, and low incidence (24 cases per 1 million people per year). Given the small number of patients with DF and, as a result, the lack of knowledge of this disease, the search for molecular predictors of the disease course and the individualization of treatment and prevention is relevant.
 Aim. To study tumor cells' molecular genetic and immunohistochemical profile and determine their clinical significance in patients with abdominal and retroperitoneal DF.
 Materials and methods. A comprehensive analysis of clinical and laboratory data of 31 patients with abdominal and retroperitoneal DF, a molecular genetic and morphological study of tumor samples was performed, including next-generation sequencing (NGS) using the Onconetix oncology panel and an immunohistochemical study using antibodies to -catenin and estrogen and progesterone receptors.
 Results. NGS testing showed somatic mutations in 28 (90%) of the 31 tumor samples. Somatic mutations in the CTNNB1 gene were detected in 26 (84%) tumor samples: 21 (68%) patients had c.121AG (p.Thr41Ala, rs121913412), 3 (10%) patients had c.134CT (p.Ser45Phe, rs121913409), 1 (3%) patient had c.133TC (p.Ser45Pro, rs121913407), and 1 (3%) patient had c.122CT (p.Thr41Ile, rs121913413). Two (6%) patients had mutations in the APC gene: c.4381GT (p.Glu1461Ter, COSM30779) and c.4634CA (p.Ser1545Ter, rs863225356). In 3 (9%) patients, no mutations were detected in the studied genes. The immunohistochemical study showed the expression of -catenin in the cytoplasm and nuclei of tumor cells in 16 (51.6%) samples. Nuclear expression of estrogen and progesterone receptors was detected in 6 (19%) and 1 (3.2%) samples, respectively. Of 10 patients with established relapses, sequencing (NGS) showed a c.121AG mutation (p.Thr41Ala, rs121913412) in 7; 1 patient had a c.134CT mutation (p.Ser45Phe, rs121913409), and 2 patients had no mutations in tumor samples.
 Conclusion. The combination of factors such as the retroperitoneal DF, the presence of the c.121AG mutation (p.Thr41Ala, rs121913412) in the CTNNB1 gene, female gender, and young age, can warrant assigning the patient to the group with an unfavorable DF prognosis.

Objective: Most pancreatic tumors are epithelial, and, among these, more than 90% are of ductal origin. However, a variety of mesenchymal tumors may involve the pancreas and may manifest different clinicopathological characteristics. The literature on mesenchymal tumors in the pancreas is largely limited to individual case reports or analyses of small series, predominantly focusing on radiologic features.Material and Method: Authors’ institutional and consultation databases were reviewed to identify the mesenchymal tumors involving the pancreas.Results: Forty cases were identified; twenty-five (63%) tumors were benign/borderline, and the remaining fifteen (37%) were malignant. Of the benign/borderline tumors; 9 were solitary fibrous tumors, 6 gastrointestinal stromal tumors (GISTs), 4 schwannomas, 2 desmoid type fibromatosis, 1 lymphangioma, 1 ganglioneuroma, 1 inflammatory myofibroblastic tumor, and 1 low grade mesenchymal neoplasm. Malignant tumors included 6 cases of leiomyosarcomas, 4 liposarcomas, 2 rhabdomyosarcomas, 1 epithelioid angiosarcoma, 1 malignant peripheral nerve sheet tumor, and 1 undifferentiated pleomorphic sarcoma. Four cases (multicystic schwannoma, desmoid fibromatosis, lymphangioma and inflammatory myofibroblastic tumor) were preoperatively misdiagnosed as a primary epithelial tumor of the pancreas.Conclusion: Mesenchymal tumors rarely involve the pancreas. They are usually benign/borderline neoplasms but may be diagnostically challenging, especially clinically/radiologically, as they may form cystic and/or large lesions in the pancreas. Mesenchymal tumors should be considered in both the clinical/radiological and pathological differential diagnosis of pancreatic lesions.

11547 Background: Recently, first-in-class FDA approval was granted in the U.S. for use of the gamma secretase inhibitor (GSI), nirogacestat, for adults with progressive desmoid fibromatosis. In tandem, the unpredictable clinical behavior of desmoids, which ranges from local aggression to regression, raises consideration of whether diagnostic and molecular variability underlie their varying biological potential. With an aim to understand both, and to explore the potential for biomarkers for GSI therapy selection, prediction, and prognosis, we performed a retrospective review of comprehensive genomic profiling and histology of desmoids and other soft tissue tumors harboring CTNNB1 or APC mutations. Methods: Using real-world reference laboratory database of tumors submitted for clinical genomic assessment (Caris Life Sciences), we queried for samples with a diagnosis of desmoid fibromatosis, or for other neoplasms of soft tissue origin harboring CTNNB1 or APC mutations. Samples underwent next-gen sequencing of (whole exome) to identify gene variants/copy number alterations and of RNA (whole transcriptome) for expression and fusion profiling. Findings were correlated with available clinical data and whole slide image histologic review. Results: We identified 74 tumors submitted as desmoid fibromatosis, of which 80% harbored CTNNB1 and 15% harbored APC pathogenic or likely pathogenic variants. CTNNB1 variants included codon 41 (58%), codon 45 (41%), and ubiquitin motif codon 36 (1%), while 91% of APC variants detected were in exon 16. Recurrent co-alterations were rare, involving MUTYH (heterozygous G396D) in 2 samples, and TMB-High (≥10 mutations/Mb) present in 3 . Notably, 4 “desmoids” (5%) lacked characteristic mutations, one of which harbored COL1A1::USP6 fusion, reclassified as nodular fasciitis. Among 76 soft tissue tumors diagnosed as other entities at analysis but found to harbor CTNNB1/APC mutations, 6 (all limited core biopsies), could be confidently reclassified as desmoids. The remaining 70 CTNNB1/APC mutant neoplasms were diverse, including synovial sarcoma (11%) and rhabdomyosarcoma (10%). Conclusions: Correlation of genomics and histopathology may allow identification of other tumor types misclassified as desmoid fibromatosis. Conversely, genomic correlation facilitated recognition of additional desmoids among tumors submitted with other diagnoses. The striking lack of secondary mutations seen in this large cohort with comprehensive DNA sequencing implies that other mechanisms explain and could predict their variable behavior, for which we are exploring paired transcriptome profiling data. Finally, subsets of diverse, other soft tissue neoplasms harbor CTNNB1 or APC mutations, which may have implications for the design of future biomarker-selected Phase II basket trials.

Introduction: Desmoid fibromatosis (DF) or Desmoid tumours are rare, benign musculoaponeurotic tumours. DF have no potential for metastatic spread but are locally aggressive and spread along fascial planes, leading to extensive patient morbidity. While germline Adenomatous Polyposis Coli (APC) mutations are associated with DF, it can also occur sporadically. Debate regarding the most appropriate treatment options exists in literature. Case summary: A 38 year old lady presented with a left hypochondrial swelling, night sweats and weight loss to the General Surgical Outpatients Department at our institution. This was noticed after the birth of her second child. No relevant family history was noted. A pre-operative ultrasound demonstrated a fusiform nodule within the left anterior abdominal transversalis oblique muscle, which had a focal hypervascular nidus. Surgical excision of the mass was performed under general anaesthetic and histologically the tumour was found to contain spindled myofibroblastic cells arranged in fascicles with perivascular lymphoid infiltrates. The diagnosis was DF with a positive margin status. Given the high risk of recurrence of this tumour type, the decision was made to undertake a further resection. Conclusion: DF is known to be a locally aggressive benign tumour of mesenchymal origin. The benefits and disadvantages of treatment options are debated within literature. Surgery is reported to have better or similar local control rates to radiotherapy but without radiation related complications. Given that DF is known to be locally aggressive, affecting young people and with a female preponderance, we believe that surgical excision with clear margins is the most appropriate treatment of choice.

10568 Background: Desmoid Fibromatosis (DF) is one of a group of rare fibrous tissue proliferations (2–4 cases per year per million) which tend to be locally aggressive but have no propensity for metastasis. Gastrointestinal Stromal Tumor (GIST) is the most common mesenchymal tumors of the gastrointestinal tract and also rare (15–20 cases per year per million). Anecdotal reports of individuals with both diseases led us to investigate the number of patients at our institute with both types of cancer and their clinical, and histopathologic features. Methods: We identified four cases of GIST associated with DF at the M. D. Anderson Cancer Center between 1995 and 2008 using an IRB-approved protocol. Two more cases were identified from the patient database at the University of Helsinki. Results: Our patients were three men and three women aged from 39 to 66. Two patients were African Americans and 3 were Caucasians. In 5 cases, the GIST was diagnosed prior to the DF while one case had both tumors synchronous at presentation. The primary site of the GIST was gastric in 4 cases and the others were jejunal and mesenteric. Three patients had their DF occur in the surgical incision site mimicking a recurrence of GIST. The 3 others were intra-abdominal DF. There were no cases of DF occurring outside of the GI tract. One GIST patient was metastatic at presentation and one developed metastasis before DF was diagnosed. In 5 cases, imatinib mesylate was administered to the patients with partial response. In all cases KIT expression was observed immunohistochemically for GIST and but not for DF. Additionally, all cases of DF but no cases of GIST were found to have beta-catenin expression by immunohistochemistry. Conclusions: Our findings suggest that concurrent DF may occur in patients with GIST. Additionally, DF may mimic the recurrence of GIST or imatinib resistance. The association of these two sarcomas should be further explored. No significant financial relationships to disclose.

Desmoid fibromatosis (DSM) is a rare, locally aggressive mesenchymal tumor genetically characterized by mutations in the CTNNB1 gene. A local control rate of up to 65‒80% for DSM is achieved with multiple modality treatments, including watchful monitoring, radiation therapy, chemotherapy, and surgery. However, several variables, such as age < 30years, extremity tumor location, and tumor size of > 10cm in diameter, are associated with poor local control rates in patients with DSM. The definitive treatments for DSM have not been established. Therefore, it is necessary to develop novel treatments for DSM. Moreover, although patient-derived tumor cell lines are potent tools for preclinical research, no DSM cell lines have been reported. Therefore, this study aimed to establish and characterize a novel DSM cell line for preclinical studies on DSM. Herein, we established the first cell line derived from a patient with DSM exhibiting poor prognostic factors (27-year-old male patient with a DSM tumor of > 10cm in diameter located at the lower extremity) and named it NCC-DSM1-C1. NCC-DSM1-C1 cells had a T41A mutation in CTNNB1 and exhibited constant proliferation, spheroid formation, and invasion capability in vitro. Screening of antitumor agents in NCC-DSM1-C1 cells showed that bortezomib and romidepsin are effective against DSM. In conclusion, we report the first officially characterized DSM cell line derived from a patient with DSM exhibiting factors associated with poor prognosis. We believe that NCC-DSM1-C1 cell line is a useful tool for developing novel treatments for DSM.

Desmoid fibromatosis (DF) is a locally aggressive soft tissue neoplasm with frequent recurrences. DF is characterized by alterations in the Wnt/β-catenin pathway, with the majority showing sporadic mutations in CTNNB1 , whereas others have germline mutations in APC . Immunohistochemical staining for β-catenin is often difficult to interpret and can be negative in up to 30% of cases. Prior studies have shown that some DFs lacking nuclear expression of β-catenin may carry activating CTNNB1 mutations. Droplet digital polymerase chain reaction (ddPCR) has been used effectively in detecting mutations in formalin-fixed, paraffin-embedded (FFPE) samples of various cancer types. In this study, we assess the diagnostic utility of ddPCR to detect CTNNB1 mutations in DF with β-catenin expression on immunohistochemistry (IHC), as well as in diagnostically challenging cases. Of the 28 DFs with nuclear β-catenin expression by IHC, 24 cases showed a CTNNB1 mutation by ddPCR using primers against the most common point mutations in CTNNB1 . The most frequent mutation was T41A (n=14; 50%), followed by S45F (n=8; 33%) and S45P (n=3;12%). We identified 8 additional (myo)fibroblastic lesions of uncertain classification, which were negative for nuclear β-catenin expression by IHC. We detected CTNNB1 mutations in 3 unknown lesions, including S45F (n=2) and S45P (n=1). ddPCR is a sensitive, rapid and cost-efficient methodology to detect common CTNNB1 mutations in DF, especially in diagnostically challenging cases.

Desmoid fibromatosis is a rare, locally aggressive fibroblastic/myofibroblastic tumor that occasionally involves children. We examined a series of pediatric desmoids for CTNNB1 mutations, seen in sporadic tumors, and APC germline mutations, associated with familial adenomatous polyposis (FAP). Forty-four desmoids in pediatric patients were identified in the pathology files of 2 large referral centers (1995-2009). Clinical charts were reviewed for history of FAP. Germline APC gene mutations were determined on blood samples from patients presenting with FAP. Immunohistochemistry for beta-catenin was performed. CTNNB1 genotyping was done by Sanger sequencing on formalin-fixed paraffin-embedded tissue. CTNNB1 mutations were observed in 29 of 44 (66%) desmoids, with 3 mutations identified: T41A (64%), S45F (29%), and S45P (7%). Germline APC mutations were present in 7 (16%) desmoid patients. Eight (18%) patients had desmoids that were wild type for CTNNB1 and had no known clinical signs or family history suspicious for FAP at the time of testing or with extended follow up (n = 6). Beta-catenin nuclear labeling was observed in 38 of 41 (92%) tested cases, 34 (89%) of which showed mutations in either CTNNB1 (n = 29) or APC (n = 5). Nuclear localization of beta-catenin was seen in the majority of pediatric desmoids and was most often associated with somatic mutations in CTNNB1. However, a significant proportion of pediatric patients harbored germline mutations in APC. Given the implications, genetic counseling is recommended for children diagnosed with desmoid tumors lacking CTNNB1 mutations because this population is enriched for FAP patients.

Desmoid fibromatosis is a mesenchymal clonal proliferation, which lacks metastatic potential. Nevertheless, it has an infiltrative growth and thus implies a high morbidity1. Although the etiology remains unclear, mutations in the B-catenin or APC genes are involved. Some risk factors include pregnancy, hormonal exposure or surgery. Desmoid fibromatosis can be sporadic (80%) or FAP-associated2. In sporadic cases, it is caused by mutations in the B-catenin (CTNNB1) gene. Whether it is FAP-associated or not should be determined, as the treatment for each condition is different. A radiologic test is essential for diagnosis, although a biopsy is necessary for confirmation. With regard to treatment, there is a wide range of different alternatives such as observation only, medical treatment or even surgery3. However, a recurrence rate that ranges from 30% to 40% have been reported in the major published series4 and thus, conservative treatment is more common nowadays. We present the case of an 82-year-old male with constitutional syndrome. A computed tomography was performed, which identified a 69 x 52mm mass in the oesophago-gastric union. A computed tomography guided biopsy was performed and the histological analysis identified a fusocellular tumor compatible with desmoid fibromatosis. Treatment was started with indomethacin. However, a control computed tomography 3 months later showed that the mass had grown. Thus, indomethacin treatment was stopped and tamoxifen treatment was started. The patient has had an excellent performance status since symptom presentation. In conclusion, desmoid tumors are rare and most are sporadic. However, they may also be associated with familial adenomatous polyposis syndrome. It must be emphasized that our patient did not have any risk factors and the anatomical location in the oesophago-gastric union is not a common location. Desmoid fibromatosis supposes a clinical challenge for diagnosis and treatment and thus, management should be individualized.

Sinonasal myxoma (SNM) is a rare, benign mesenchymal neoplasm with distinct clinicopathologic features and aberrant nuclear localization of β-catenin by immunohistochemistry. The molecular underpinnings have been linked to that of a "myxoid variant" of desmoid fibromatosis. Herein, we describe a series of 8 cases of SNM and propose clinical and biologic differences compared with desmoid fibromatosis. Our patient cohort is comprised of 5 males and 3 females (age range: 10mo to 12y), 6 of whom are aged less than or equal to 24 months. All presented with facial swelling, reflecting lesions involving the maxillary bone, and all underwent resection. All tumors were variably cellular and comprised of bland spindled to stellate cells in a profusely myxoid background with diffuse nuclear β-catenin expression. All cases of SNM were analyzed by next-generation sequencing using the Oncopanel assay. Three cases failed sequencing, 2 of 5 successful cases exhibited exon 3 CTNNB1 alterations involving the ubiquitin recognition motif, and 3 had adenomatous polyposis coli ( APC ) deletions. One patient had APC germline testing which was negative. No germline testing was available for the remaining 7 patients. Follow-up data over a range of 1 month to 23 years was available for 7 of the 8 SNMs. One case patient had local recurrence, and all were alive without evidence of disease. This is in contrast to the high recurrence rate typically seen in desmoid fibromatosis, particularly after resection. Our findings expand the spectrum of tumors with underlying WNT/β-catenin pathway and highlight the histologic, clinical, and genetic differences of SNM compared with desmoid fibromatosis. APC deletion raises the possibility of underlying germline alteration and familial adenomatous polyposis.

Desmoid fibromatosis is a locally aggressive clonal fibroblastic proliferation with high recurrence rates and no metastatic potential. Implicated molecular aberrations occur within the Wnt/β-catenin pathway (APC and β-catenin gene mutations). Transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) are profibrotic growth factors, downstream from nuclear translocation of β-catenin, that lead to increased fibrogenesis. CTGF (a downstream effector of TGF-β) is a matricellular protein that modulates the activity of growth factors, adhesion molecules, integrins, and extracellular matrix thus playing a central role in tissue remodeling and fibrosis. Recently there has been growing interest in use of extracellular matrix inhibitors for treatment of various fibrogenic diseases. Desmoid fibromatosis samples (n=15) were evaluated for expression of β-catenin, TGF-β, and CTGF using immunohistochemistry on formalin paraffin-embedded material. A control group comprising scar tissue and adjacent normal skin (n=10) were simultaneously immunostained with above mentioned markers. Real-time polymerase chain reaction was performed on frozen specimens of desmoid fibromatosis (n=6) and normal skin (n=2). All 15 desmoid tumors were positive for β-catenin (surrogate marker of Wnt/β-catenin pathway dysregulation) which was negative in control normal skin and scar samples. TGF-β and CTGF were negative in 9 of 10 normal skin controls. TGF-β and CTGF were positive in all cases of scar tissue. All 15 cases of desmoid tumors were positive for TGF-β and CTGF. The real-time polymerase chain reaction showed higher expression levels of TGF-β and CTGF in desmoid fibromatosis compared with normal skin. The high constitutive expression of β-catenin downstream effectors; TGF-β, CTGF has the potential for enabling targeted therapy.

The article presents a rare form of pathological neoplasms — breast desmoid type fibromatosis. There are etiology and pathogenesis of the disease, clinical and morphological features, diagnostics and tactics of treatment of the disease. Widely covered clinical examples from the practice of a surgeon-oncologist. Desmoid fibromatosis (DF) is an aggressive non-metastatic mesenchymal formation that arises from musculoponeurotic structures. DF accounts for 0.03 % to 0.1 % of solid tumors and 3 % of mesenchymal tumors. Among breast pathology, this neoplasm is even rarer (0.2 %). Due to the rarity of such pathology, clinicians are not always able to correctly interpret the diagnostic picture and recognize the disease. The etiology and pathogenesis of the disease are also not fully understood, and therefore there are no standards for the treatment of desmoid fibromatosis. Surgical treatment remains the main one. To reduce the frequency of recurrence of the disease, the surgeon needs to achieve clean edges of the resection. Radiation therapy, hormone therapy, targeted therapy, and chemotherapy may additionally be considered as an alternative type of treatment. When the clean edges of the resection are reached, strict dynamic monitoring of pa is considered as further treatment.

Gardner fibroma represents a rare and recently described soft tissue tumor entity in children and young adults. It consists of haphazardly arranged coarse and hyalinized collagen fibers combined with loosely arranged bland spindle and fibroblastic cells. The case of a 13-year-old male patient with Gardner fibroma and osteoma and multicentric desmoid type fibromatosis in his mother is presented with detection of a (heterozygotic) germline mutation of the APC gene leading to a de novo stop codon (deletion of base pairs 5033-5036). FISH analysis revealed a structural loss of heterozygosity (LOH) in the APC gene on chromosomal locus 5q21 in one out of five analysed desmoids of the mother, no LOH of APC gene in the Gardner fibroma. Gardner fibroma in children and young adults may serve as an indicator lesion for familial adenomatous polyposis (FAP), Gardner syndrome, a familial desmoid type fibromatosis without other manifestations of APC or a new APC gene mutation. For the clinician, this diagnosis should be commented upon accordingly by the surgical pathologist. As the result of a detected APC gene mutation, continuous follow-up for the development of colorectal tumors and desmoid type fibromatosis as well as a familial screening for FAP is recommended.

BACKGROUND Familial adenomatous polyposis (FAP) is an autosomal-dominant dominant Familial Cancer Syndrome FCs Caused by Germline inactivation of adenomatous polyposis coli (APC) tumor suppressor gene, results in up-regulation of the WNT signaling pathway which increases the risk of colorectal cancer CRC, colon polyposis and extracolonic tumors like gastric and duodenal carcinomas WNT-activated Medulloblastoma MBL and Desmoid fibromatosis (DF) DF are locally aggressive soft tissue tumors with high local recurrence rates after Surgical excision role of adjuvant chemotherapy or Radiotherapy is still unclear. METHODS A 6-year-old boy product of non-consanguineous marriage with positive family HX brain tumor Diagnosed with Non-Metastatic Average Risk MBL WHO grade IV classic histology, he had craniotomy and Gross tumor resection followed by craniospinal irradiation at 23.4 Gy, plus a boost to posterior fossa/tumor bed up to 54 Gy, followed by 8 maintenance chemotherapy cycles as HIT-MED protocol Cisplatin/VCR/CCNU total. 3 years post end of therapy the pateint was in complete remission from MBL when routing MRI surveillance showed a new left paravertebral muscle lesion within the irradiation field from T1 to T4 levels which progressed gradually over a short follow-up time he had surgical resection of the tumor with Pathological diagnosis of Desmoid fibromatosis. after six months he had a second recurrence of the spinal tumor that needed a second surgical resection. Result: positive Genetic testing for Germline pathogenic mutation of APC gene exons 7 to 16 confirmed the diagnosis of autosomal familial adenomatous polyposis type 1(FAP1). Up to date, he is stable on endoscopic and MRI surveillance with radiological evidence of slow progression of the paraspinal tumor CONCLUSION Medulloblastomas associated with APC germline mutation have favorable outcomes that may need de-escalating therapeutic protocol with reduced intensity craniospinal irradiation aiming to reduce the incidence of secondary tumors after adjuvant treatment for MBL

Desmoid-type fibromatosis: from morphology to molecular genetics