Predominance of beta-catenin mutations and beta-catenin dysregulation in sporadic aggressive fibromatosis (desmoid tumor)

The role of Dickkopf-1 in joint remodeling and fibrosis: A link connecting spondyloarthropathies and scleroderma?

BACKGROUND

Dickkopf-1 (Dkk-1) is a soluble inhibitor of the canonical Wnt pathway, which plays critical roles in embryonic development. Evidence suggests that this molecule regulates several aspects of both bone biology and fibrosis.

OBJECTIVES

To provide an overview of our current knowledge of the role of Dkk-1 in joint remodeling and fibrosis.

METHODS

We performed an electronic search (Medline) using the following key words: Dickkopf-1 (or Dkk-1), new bone formation, joint remodeling, ankylosing spondylitis, systemic sclerosis (or scleroderma), and fibrosis, supplemented by a manual search of references from retrieved articles.

RESULTS

Dkk-1 is a master regulator of joint remodeling in animal models of arthritis shifting the balance toward new bone formation when its expression is decreased and toward erosion/joint destruction when its expression is increased. In humans, evidence suggests that Dkk-1 may be dysfunctional in patients with ankylosing spondylitis, a prototype bone forming disease. Moreover, data from animal models indicate that Dkk-1 has a protective role against fibrosis in several organs. Recent data suggest that inhibiting the canonical Wnt pathway by overexpression of Dkk-1 could be a way to target TGF-β signaling in fibrotic diseases. Finally, B-cell depletion therapy in systemic sclerosis may exert its effects through TGF-β dependent upregulation of Dkk-1.

CONCLUSIONS

Dkk-1 appears to play a crucial role in both joint remodeling/ectopic ossification and fibrosis, and may be a prospective therapeutic modality for fibrotic diseases or diseases characterized by pathologic joint remodeling.

Mesenchymal Tumors Can Derive from Ng2/Cspg4-Expressing Pericytes with β-Catenin Modulating the Neoplastic Phenotype

The cell of origin for most mesenchymal tumors is unclear. One cell type that contributes to this lineages is the pericyte, a cell expressing Ng2/Cspg4. Using lineage tracing, we demonstrated that bone and soft tissue sarcomas driven by the deletion of the Trp53 tumor suppressor, or desmoid tumors driven by a mutation in Apc, can derive from cells expressing Ng2/Cspg4. Deletion of the Trp53 tumor suppressor gene in these cells resulted in the bone and soft tissue sarcomas that closely resemble human sarcomas, while stabilizing β-catenin in this same cell type caused desmoid tumors. Comparing expression between Ng2/Cspg4-expressing pericytes lacking Trp53 and sarcomas that arose from deletion of Trp53 showed inhibition of β-catenin signaling in the sarcomas. Activation of β-catenin inhibited the formation and growth of sarcomas. Thus, pericytes can be a cell of origin for mesenchymal tumors, and β-catenin dysregulation plays an important role in the neoplastic phenotype.

Primary and recurrent sporadic desmoids: Prognostic factors influencing recurrence-free survival after complete gross resection

INTRODUCTION

There is continuing controversy over the significance of prognostic factors in sporadic desmoid-type fibromatosis (DF). Further, only limited data is available in the literature concerning second recurrence in patients with recurrent DF. The purpose of this study was to identify prognostic factors influencing recurrence-free survival (RFS) and to determine rates of local recurrence (LR) in patients with primary and recurrent DF.

METHODS

Fifty-three consecutive patients with DF who underwent surgery at a single institution were identified. As a result of strict exclusion criteria, a homogeneous cohort of thirty-two patients who received macroscopically complete resection was included in this study and split into a primary (PG) and recurrent disease (RG) group. Clinicopathological parameters and immunohistochemical markers were retrospectively and independently analyzed in both groups.

RESULTS

The local recurrence rate was 35% for the PG and 33% for the RG. The PG's calculated median time to relapse was 17 months, and the RG's was 29 months. The estimated 1-, 5-, and 8-year RFS rates for the PG were 75%, 64%, and 55% while the corresponding RFS rates for the RG were 69%, 69%, and 52%, respectively. In primary disease, extraabdominal tumor location was the only significant adverse prognostic factor associated with worse RFS (p = 0.008). Whereas in recurrent disease, age ≥40 yrs (p = 0.022) and R0 margin status (p = 0.049) correlated with a significantly better outcome.

CONCLUSION

Recurrence in primary and recurrent DF is characterized by different predictive factors and benefits from distinct therapeutic strategies. Immunohistochemical markers are valuable tools in the diagnosis of DF, although have limited potential in predicting the outcome.

Resection and Abdominal Wall Reconstruction of a Desmoid Tumor with Endometrioma Features

Desmoid tumors are rare, musculoaponeurotic mesenchymal origin tumors arising from the proliferation of well-differentiated fibroblasts. Desmoid tumors may arise from any location with the abdominal cavity, abdominal wall and extremity locations being most frequent. We present the case of a 35-year-old female with a history of endometriosis who presented palpable abdominal mass and cyclic abdominal pain. Resection was performed for a presumed desmoid soft tissue tumor. Final pathology demonstrated desmoid histology admixed with abdominal wall endometriosis (endometrioma). This unique pathologic finding has only been rarely reported and is discussed with a brief review of the literature.

Clinical significance of midkine expression in sporadic desmoid tumors

The aim of the present study was to identify the prognostic factors for the propensity for recurrence in sporadic desmoid tumors. The catenin (cadherin-associated protein) β1 (CTNNB1) genotypes and expression of Wnt pathway proteins and midkine (also termed neurite growth-promoting factor 2) were investigated in 159 patients with sporadic desmoid tumors. Formalin-fixed paraffin-embedded tissues of the surgically resected desmoid tumors were examined by direct sequencing of CTNNB1 exon 3, and immunostained for the expression of β-catenin, T-cell factor 4 (TCF-4), phosphorylated protein kinase B (pAkt), midkine and menin using a tissue microarray method. Among the samples, 70% (111/159) exhibited point mutations of the CTNNB1 gene, including T41A (56%), S45F (8%), S45P (2%), S45N (2%) and T42A (1%). In addition, 100, 57, 24, 15 and 92% of the tumors expressed β-catenin, TCF-4, midkine, pAkt and menin, respectively. Positive midkine expression was significantly associated with the recurrence of tumors (P=0.001). The multivariate analysis of recurrence demonstrated that an extra-abdominal tumor site [hazard ratio (HR), 2.625; P=0.001] and midkine expression (HR, 2.077; P<0.009) were independent prognostic factors of tumor recurrence. In conclusion, the present results suggest that the tumor site and midkine expression may be predictive markers for the recurrence of sporadic desmoid tumors.

CTNNB1 (β-Catenin)-altered Neoplasia: A Review Focusing on Soft Tissue Neoplasms and Parenchymal Lesions of Uncertain Histogenesis

β-catenin (CTNNB1) is a key regulatory molecule of the Wnt signaling pathway, which is important for tissue homeostasis and regulation of cell proliferation, differentiation, and function. Abnormal stabilization and nuclear accumulation of β-catenin as a consequence of missense mutations or alternative molecular mechanisms occurs at a high frequency in a variety of epithelial cancers. In mesenchymal neoplasia, the role of β-catenin has been traditionally considered limited to desmoid-type fibromatosis. However, the spectrum of β-catenin-driven (β-catenin-altered) neoplasia of mesenchymal origin has been steadily widening to include, in addition to desmoid tumors, a variety of benign and intermediate-biology neoplasms of soft tissue (intranodal palisaded myofibroblastoma), head and neck (juvenile nasopharyngeal angiofibroma and sinonasal hemangiopericytoma/glomangiopericytoma), and ovarian (microcystic stromal tumor) origin. In addition, several old and newly reported distinctive site-specific β-catenin-driven parenchymal neoplasms of uncertain histogenesis have been well characterized in recent studies, including solid-pseudopapillary neoplasm of the pancreas and its recently described ovarian counterpart, sclerosing hemangioma of lung and calcifying nested stromal-epithelial tumor of the liver. This review addresses the most relevant pathobiological and differential diagnostic aspects of β-catenin-altered neoplasms with emphasis on site-specific histologic and biological variations. In addition, the morphologic overlap and analogy as well as distinctness between these uncommon tumors will be presented and discussed. Furthermore, a note is made on association of some of these lesions with hereditary tumor syndromes, in particular with the familial adenomatous polyposis coli.

Spatio-temporal genetic heterogeneity of CTNNB1 mutations in sporadic desmoid type fibromatosis lesions

Desmoid type fibromatosis (DT) is a rare lesion of unclear pathogenesis that most often presents a mutation of the (β-catenin) gene. The natural history and clinical evolution are highly variable between patients and to date there is no consensus on optimal therapy. We report two cases of a patient with multiple DT lesions. Molecular investigations performed in both patients on multiple tumors at different anatomical sites revealed non-identical CTNNB1 mutations. The first patient was a 39-year-old man with a history of recurrent DT. In two of the DT lesions, three different mutations were found in codons 41 and 45, respectively. The lesions showed marked inflammatory features, characterized by IgG4 positive lymphoplasmacytic infiltrates and a foreign body reaction, which increased in intensity over time. The patient was eventually treated with a COX-2 inhibitor and the remaining mass was stabilized. In the two DT lesions of the second patient, CTNNB1 mutations S45P and T41A were found. The presence of different mutations in multiple focally recurrent sporadic DT lesions indicates that they do not have a clonal relationship. Our data suggest that a CTNNB1 mutation is a necessary event probably by providing a selective growth advantage. An IgG4 host antigen response is discussed as a potential predisposing factor for one of the patients.

Inhibition of Wnt/β-catenin pathway promotes regenerative repair of cutaneous and cartilage injury

Wound healing in mammals is a fibrotic process. The mechanisms driving fibrotic (as opposed to regenerative) repair are poorly understood. Herein we report that therapeutic Wnt inhibition with topical application of small-molecule Wnt inhibitors can reduce fibrosis and promote regenerative cutaneous wound repair. In the naturally stented model of ear punch injury, we found that Wnt/β-catenin pathway is activated most notably in the dermis of the wound bed early (d 2) after injury and subsides to baseline levels by d10. Topical application of either of 2 mechanistically distinct small-molecule Wnt pathway inhibitors (a tankyrase inhibitor, XAV-939, and the U.S. Food and Drug Administration-approved casein kinase activator, pyrvinium) in C57Bl/6J mice resulted in significantly increased rates of wound closure (72.3 ± 14.7% with XAV-939; and 52.1 ± 20.9% with pyrvinium) compared with contralateral controls (38.1 ± 23.0 and 40.4.± 16.7%, respectively). Histologically, Wnt inhibition reduced fibrosis as measured by α-smooth muscle actin positive myofibroblasts and collagen type I α1 synthesis. Wnt inhibition also restored skin architecture including adnexal structures in ear wounds and dermal-epidermal junction with rete pegs in excisional wounds. Additionally, in ear punch injury Wnt inhibitor treatment enabled regeneration of auricular cartilage. Our study shows that pharmacologic Wnt inhibition holds therapeutic utility for regenerative repair of cutaneous wounds.

Intrathoracic Desmoid Tumor Presenting as Multiple Lung Nodules 13 Years after Previous Resection of Abdominal Wall Desmoid Tumor

Desmoid tumors are rare soft tissue tumors considered to have locally infiltrative features without distant metastasis until now. Although they are most commonly intraabdominal, very few cases have extra-abdominal locations. The origin of intrathoracic desmoid tumors is predominantly the chest wall with occasional involvement of pleura. True intrathoracic primary desmoid tumors with no involvement of the chest wall or pleura are extremely rare. We recently experienced a case of true intrathoracic desmoid tumor presenting as multiple lung nodules at 13 years after resection of a previous intraabdominal desmoid tumor.

Near universal detection of alterations in CTNNB1 and Wnt pathway regulators in desmoid-type fibromatosis by whole-exome sequencing and genomic analysis

CTNNB1 mutations or APC abnormalities have been observed in ∼85% of desmoids examined by Sanger sequencing and are associated with Wnt/β-catenin activation. We sought to identify molecular aberrations in "wild-type" tumors (those without CTNNB1 or APC alteration) and to determine their prognostic relevance. CTNNB1 was examined by Sanger sequencing in 117 desmoids; a mutation was observed in 101 (86%) and 16 were wild type. Wild-type status did not associate with tumor recurrence. Moreover, in unsupervised clustering based on U133A-derived gene expression profiles, wild-type and mutated tumors clustered together. Whole-exome sequencing of eight of the wild-type desmoids revealed that three had a CTNNB1 mutation that had been undetected by Sanger sequencing. The mutation was found in a mean 16% of reads (vs. 37% for mutations identified by Sanger). Of the other five wild-type tumors sequenced, two had APC loss, two had chromosome 6 loss, and one had mutation of BMI1. The finding of low-frequency CTNNB1 mutation or APC loss in wild-type desmoids was validated in the remaining eight wild-type desmoids; directed miSeq identified low-frequency CTNNB1 mutation in four and comparative genomic hybridization identified APC loss in one. These results demonstrate that mutations affecting CTNNB1 or APC occur more frequently in desmoids than previously recognized (111 of 117; 95%), and designation of wild-type genotype is largely determined by sensitivity of detection methods. Even true CTNNB1 wild-type tumors (determined by next-generation sequencing) may have genomic alterations associated with Wnt activation (chromosome 6 loss/BMI1 mutation), supporting Wnt/β-catenin activation as the common pathway governing desmoid initiation.

Contralateral recurrence of aggressive fibromatosis in a young woman: A case report and review of the literature

Aggressive fibromatosis (AF) is a benign non-encapsulated tumor of mesenchymal origin, with a tendency for local spread along fascial planes. Local invasion can lead to extensive morbidity and even mortality due to destruction of the bones, organs and soft tissues. This rare lesion is observed 1,000 times more frequently in patients with familial adenomatous polyposis or Gardner's syndrome due to the inheritance of the adenomatous polyposis coli (APC) gene. While AF does not metastasize, local recurrence is common. Distant recurrence is extremely rare, but is observed in those with a germ line APC mutation. The present study details the case of a 20-year-old woman with a melanoma of the right shoulder, treated definitively with surgery. The patient then developed a painful mass at the surgical site; a surgical biopsy demonstrated that the mass was AF. The patient was treated with surgical resection, radiation therapy, and a course of tamoxifen. Five years later, the patient presented with left forearm pain and diminished range of motion due to an infiltrating mass. This was excised and a clinical diagnosis of recurrent AF was made, in this patient lacking familial predisposition to the disease.

Nuclear expression and gain-of-function β-catenin mutation in glomangiopericytoma (sinonasal-type hemangiopericytoma): insight into pathogenesis and a diagnostic marker

Glomangiopericytoma (sinonasal-type hemangiopericytoma) is a rare mesenchymal neoplasm with myoid phenotype (smooth muscle actin-positive), which distinguishes this tumor from soft tissue hemangiopericytoma/solitary fibrous tumor. Molecular genetic changes underlying the pathogenesis of glomangiopericytoma are not known. In this study, 13 well-characterized glomangiopericytomas were immunohistochemically evaluated for β-catenin expression. All analyzed tumors showed strong expression and nuclear accumulation of β-catenin. Following this observation, β-catenin glycogen serine kinase-3 beta phosphorylation region, encoded by exon 3, was PCR amplified in all cases and evaluated for mutations using Sanger sequencing. Heterozygous mutations were identified in 12 of 13 tumors. All mutations consisted of single-nucleotide substitutions: three in codon 32 (c.94G>C (n=2) and c.95A>T), four in codon 33 (two each c.98C>G and c.98C>T), two in codon 37 (c.109T>G), one in codon 41 (c.121A>G), and two in codon 45 (c.133T>C). At the protein level, these substitutions would lead to p.D32H, p.D32V, p.S33C, p.S33F, p.S37A, p.T41A, and p.S45L mutations, respectively. Previously, similar mutations have been reported in different types of cancers and shown to trigger activation of β-catenin signaling. All analyzed glomangiopericytomas showed prominent nuclear expression of cyclin D1, as previously shown for tumors with nuclear expression of β-catenin as a sign of oncogenic activation. These results demonstrate that mutational activation of β-catenin and associated cyclin D1 overexpression may be central events in the pathogenesis of glomangiopericytoma. In additon, nuclear accumulation of β-catenin is a diagnostic marker for glomangiopericytoma.

Next-generation sequencing is highly sensitive for the detection of beta-catenin mutations in desmoid-type fibromatoses

Desmoid-type fibromatoses are locally aggressive and frequently recurrent tumours, and an accurate diagnosis is essential for patient management. The majority of sporadic lesions harbour beta-catenin (CTNNB1) mutations. We used next-generation sequencing to detect CTNNB1 mutations and to compare the sensitivity and specificity of next-generation sequencing with currently employed mutation detection techniques: mutation-specific restriction enzyme digestion and polymerase chain reaction amplification. DNA was extracted from formalin-fixed paraffin-embedded needle biopsy or resection tissue sections from 144 patients with sporadic desmoid-type fibromatoses, four patients with syndrome-related desmoid-type fibromatoses and 11 morphological mimics. Two primer pairs were designed for CTNNB1 mutation hotspots. Using ≥10 ng of DNA, libraries were generated by Fluidigm and sequenced on the Ion Torrent Personal Genome Machine. Next-generation sequencing had a sensitivity of 92.36 % (133/144, 95 % CIs: 86.74 to 96.12 %) and a specificity of 100 % for the detection of CTNNB1 mutations in desmoid-type fibromatoses-like spindle cell lesions. All mutations detected by mutation-specific restriction enzyme digestion were identified by next-generation sequencing. Next-generation sequencing identified additional mutations in 11 tumours that were not detected by mutation-specific restriction enzyme digestion, two of which have not been previously described. Next-generation sequencing is highly sensitive for the detection of CTNNB1 mutations. This multiplex assay has the advantage of detecting additional mutations compared to those detected by mutation-specific restriction enzyme digestion (sensitivity 82.41 %). The technology requires minimal DNA and is time- and cost-efficient.

The GSK-3 family as therapeutic target for myocardial diseases

Glycogen synthase kinase-3 (GSK-3) is one of the few signaling molecules that regulate a truly astonishing number of critical intracellular signaling pathways. It has been implicated in several diseases including heart failure, bipolar disorder, diabetes mellitus, Alzheimer disease, aging, inflammation, and cancer. Furthermore, a recent clinical trial has validated the feasibility of targeting GSK-3 with small molecule inhibitors for human diseases. In the current review, we will focus on its expanding role in the heart, concentrating primarily on recent studies that have used cardiomyocyte- and fibroblast-specific conditional gene deletion in mouse models. We will highlight the role of the GSK-3 isoforms in various pathological conditions including myocardial aging, ischemic injury, myocardial fibrosis, and cardiomyocyte proliferation. We will discuss our recent findings that deletion of GSK-3α specifically in cardiomyocytes attenuates ventricular remodeling and cardiac dysfunction after myocardial infarction by limiting scar expansion and promoting cardiomyocyte proliferation. The recent emergence of GSK-3β as a regulator of myocardial fibrosis will also be discussed. We will review our recent findings that specific deletion of GSK-3β in cardiac fibroblasts leads to fibrogenesis, left ventricular dysfunction, and excessive scarring in the ischemic heart. Finally, we will examine the underlying mechanisms that drive the aberrant myocardial fibrosis in the models in which GSK-3β is specifically deleted in cardiac fibroblasts. We will summarize these recent results and offer explanations, whenever possible, and hypotheses when not. For these studies we will rely heavily on our models and those of others to reconcile some of the apparent inconsistencies in the literature.

Intranodal palisaded myofibroblastoma: another mesenchymal neoplasm with CTNNB1 (β-catenin gene) mutations: clinicopathologic, immunohistochemical, and molecular genetic study of 18 cases

Intranodal palisaded myofibroblastoma is a benign, lymph node-based myofibroblastic tumor of unknown pathogenesis. We report the clinicopathologic, immunohistochemical, and molecular genetic features of this rare entity. The study cohort consisted of 14 men and 4 women ranging in age from 31 to 65 (mean, 47; median 49) years with tumors arising in inguinal lymph nodes (n=15), a neck lymph node (n=1), and undesignated lymph nodes (n=2). Most individuals presented with a painless mass or lump. Possible trauma/injury to the inguinal region was documented in 4 cases. Tumors ranged in size from 1.0 to 4.2 (mean, 3.1; median; 3.0) cm. Microscopically, the process presented as a well-circumscribed, oftentimes pseudoencapsulated nodule (n=17) or nodules (n=1). Tumors consisted of a cellular proliferation of cytologically bland, spindled cells arranged in short fascicles and whorls within a finely collagenous (n=11) or myxocollagenous (n=7) matrix. In 12 tumors, scattered fibromatosis-like fascicles of spindled cells were noted. Histologic features characteristic of the process included nuclear palisades (n=16 cases), collagenous bodies (n=15), and perinuclear intracytoplasmic hyaline globules (n=10). Mitotic activity ranged from 0 to 8 (mean, 2; median, 1) mitotic figures/50 high-powered fields with no atypical division figures identified. Immunohistochemically, all tumors tested expressed smooth muscle actin and/or muscle-specific actin (n=5, each), and nuclear β-catenin and cyclin D1 (n=8, each). The latter 2 results prompted a screening for mutations in the β-catenin gene glycogen synthase kinase-3 β phosphorylation mutational "hotspot" region in exon 3 using polymerase chain reaction amplification and Sanger sequencing. Single nucleotide substitutions leading to missense mutations at the protein level were identified in 7 of 8 (88%) analyzed tumors and are responsible for the abnormal expression of β-catenin and cyclin D1. These results demonstrate that mutational activation of the β-catenin gene is likely a pivotal event in the pathogenesis of intranodal palisaded myofibroblastoma.

The Wnt/β-catenin pathway in human fibrotic-like diseases and its eligibility as a therapeutic target

The canonical Wnt signaling pathway is involved in a variety of biological processes like cell proliferation, cell polarity, and cell fate determination. This pathway has been extensively investigated as its deregulation is linked to different diseases, including various types of cancer, skeletal defects, birth defect disorders (including neural tube defects), metabolic diseases, neurodegenerative disorders and several fibrotic diseases like desmoid tumors. In the "on state", beta-catenin, the key effector of Wnt signaling, enters the nucleus where it binds to the members of the TCF-LEF family of transcription factors and exerts its effect on gene transcription. Disease development can be caused by direct or indirect alterations of the Wnt/β-catenin signaling.

In the first case germline or somatic mutations of the Wnt components are associated to several diseases such as the familial adenomatous polyposis (FAP) - caused by germline mutations of the tumor suppressor adenomatous polyposis coli gene (APC) - and the desmoid-like fibromatosis, a sporadic tumor associated with somatic mutations of the β-catenin gene (CTNNB1).

In the second case, epigenetic modifications and microenvironmental factors have been demonstrated to play a key role in Wnt pathway activation. The natural autocrine Wnt signaling acts through agonists and antagonists competing for the Wnt receptors. Anomalies in this regulation, whichever is their etiology, are an important part in the pathogenesis of Wnt pathway linked diseases. An example is promoter hypermethylation of Wnt antagonists, such as SFRPs, that causes gene silencing preventing their function and consequently leading to the activation of the Wnt pathway. Microenvironmental factors, such as the extracellular matrix, growth factors and inflammatory mediators, represent another type of indirect mechanism that influence Wnt pathway activation. A favorable microenvironment can lead to aberrant fibroblasts activation and accumulation of ECM proteins with subsequent tissue fibrosis that can evolve in fibrotic disease or tumor.

Since the development and progression of several diseases is the outcome of the Wnt pathway cross-talk with other signaling pathways and inflammatory factors, it is important to consider not only direct inhibitors of the Wnt signaling pathway but also inhibitors of microenvironmental factors as promising therapeutic approaches for several tumors of fibrotic origin.

The Wnt/β-catenin pathway in human fibrotic-like diseases and its eligibility as a therapeutic target

The canonical Wnt signaling pathway is involved in a variety of biological processes like cell proliferation, cell polarity, and cell fate determination. This pathway has been extensively investigated as its deregulation is linked to different diseases, including various types of cancer, skeletal defects, birth defect disorders (including neural tube defects), metabolic diseases, neurodegenerative disorders and several fibrotic diseases like desmoid tumors. In the "on state", beta-catenin, the key effector of Wnt signaling, enters the nucleus where it binds to the members of the TCF-LEF family of transcription factors and exerts its effect on gene transcription. Disease development can be caused by direct or indirect alterations of the Wnt/β-catenin signaling. In the first case germline or somatic mutations of the Wnt components are associated to several diseases such as the familial adenomatous polyposis (FAP) - caused by germline mutations of the tumor suppressor adenomatous polyposis coli gene (APC) - and the desmoid-like fibromatosis, a sporadic tumor associated with somatic mutations of the β-catenin gene (CTNNB1). In the second case, epigenetic modifications and microenvironmental factors have been demonstrated to play a key role in Wnt pathway activation. The natural autocrine Wnt signaling acts through agonists and antagonists competing for the Wnt receptors. Anomalies in this regulation, whichever is their etiology, are an important part in the pathogenesis of Wnt pathway linked diseases. An example is promoter hypermethylation of Wnt antagonists, such as SFRPs, that causes gene silencing preventing their function and consequently leading to the activation of the Wnt pathway. Microenvironmental factors, such as the extracellular matrix, growth factors and inflammatory mediators, represent another type of indirect mechanism that influence Wnt pathway activation. A favorable microenvironment can lead to aberrant fibroblasts activation and accumulation of ECM proteins with subsequent tissue fibrosis that can evolve in fibrotic disease or tumor. Since the development and progression of several diseases is the outcome of the Wnt pathway cross-talk with other signaling pathways and inflammatory factors, it is important to consider not only direct inhibitors of the Wnt signaling pathway but also inhibitors of microenvironmental factors as promising therapeutic approaches for several tumors of fibrotic origin.

Advances in therapy for pediatric sarcomas

Pediatric sarcomas are relatively rare malignancies individually. As a group they are typically approached with combination chemotherapies in addition to local control. Fortunately, these malignancies have been approached through careful clinical trial collaboration to define risk groups and appropriately deliver local control measures and systemic therapies. Although local disease is typically approached with curative intent, therapy typically lasts over 6 months and has significant associated morbidities. It is more difficult to cure metastatic disease or induce sustained remissions. In this article, we discuss recent advances in the understanding of the disease process and highlight recent and future cooperative group trials in osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, nonrhabdomyosarcoma soft tissue sarcomas, and desmoid tumor as well as discuss promising therapeutic approaches such as epigenetics and immunotherapy.

Identification of novel therapeutic targets in the PI3K/AKT/mTOR pathway in hepatocellular carcinoma using targeted next generation sequencing

Understanding genetic aberrations in cancer leads to discovery of new targets for cancer therapies. The genomic landscape of hepatocellular carcinoma (HCC) has not been fully described. Therefore, patients with refractory advanced/metastatic HCC referred for experimental therapies, who had adequate tumor tissue available, had targeted next generation sequencing (NGS) of their tumor samples using the Illumina HiSeq 2000 platform (Foundation One, Foundation Medicine, MA) and their treatment outcomes were analyzed. In total, NGS was obtained for 14 patients (median number of prior therapies, 1) with advanced/metastatic HCC. Of these 14 patients, 10 (71%) were men, 4 (29%) women, 6 (43%) had hepatitis B or C-related HCC. NGS revealed at least 1 molecular abnormality in 12 patients (range 0-8, median 2). Detected molecular aberrations led to putative activation of the PI3K/AKT/mTOR pathway (n=3 [mTOR, PIK3CA, NF1]), Wnt pathway (n=6 [CTNNA1, CTNNB1]), MAPK pathway (n=2 [MAP2K1, NRAS]), and aberrant DNA repair mechanisms, cell cycle control and apoptosis (n=18 [ATM, ATR, BAP1, CCND1, CDKN2A, CDK4, FGF3, FGF4, FGF19, MCL1, MDM2, RB1, TP53]). Of the 3 patients with molecular aberrations putatively activating the PI3K/AKT/mTOR pathway, 2 received therapies including a mTOR inhibitor and all demonstrated therapeutic benefit ranging from a partial response to minor shrinkage per RECIST (-30%, -15%; respectively). In conclusion, genomic alterations are common in advanced HCC. Refractory patients with alterations putatively activating the PI3K/AKT/mTOR pathway demonstrated early signals of clinical activity when treated with therapies targeting mTOR.

Enhancement of Runx2 expression is potentially linked to β-catenin accumulation in canine intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) greatly affects the quality of life. The nucleus pulposus (NP) of chondrodystrophic dog breeds (CDBs) is similar to the human NP because the cells disappear with age and are replaced by fibrochondrocyte-like cells. Because IVDD develops as early as within the first year of life, we used canines as a model to investigate the in vitro mechanisms underlying IVDD. The mechanism underlying age-related IVDD, however, is poorly understood. Several research groups have suggested that Wnt/β-catenin signaling plays an important role in IVDD. However, the role of Wnt/β-catenin signals in IVD cells is not yet well understood. Here, we demonstrate that Wnt/β-catenin signaling could enhance Runx2 expression in IVDD and lead to IVD calcification. Nucleus pulposus (NP) tissue was obtained from Beagle dogs after evaluation of the degeneration based on magnetic resonance imaging (MRI). Histological analysis showed that lack of Safranin-O staining, calcified area, and matrix metalloproteinase (MMP) 13-positive cells increased with progression of the degeneration. Furthermore, the levels of β-catenin- and Runx2-positive cells also increased. Real-time reverse-transcription polymerase chain reaction analysis showed that the MRI signal intensity and mRNA expression levels of β-catenin and Runx2 are correlated in NP tissues. Moreover, supplementation of LiCl induced β-catenin accumulation and Runx2 expression. In contrast, FH535 inhibited LiCl-induced upregulation. These results suggest that Runx2 transcript and protein expression, potentially in combination with β-catenin accumulation, are enhanced in degenerated and calcified intervertebral discs of CDBs.

Desmoid tumours: our experience of six cases and review of literature

Desmoid tumours represent aggressive fibroblastic proliferation of the musculoaponeurotic structures commonly from the anterior abdominal wall. These tumours infiltrate locally, recur frequently but do not metastasize. Antecedent trauma, pregnancy and estrogens play a role in the etiopathogenesis of these tumours. In familial adenomatous polyposis (FAP) genetic history associated with chromosomal abnormality and familial incidence as in Gardner's syndrome is reported and most of these tumours are intraperitoneal either in the mesentery or pelvis and may be multiple and they carry poor prognosis. Surgery is the most preferred treatment and requires wide excision with 1 cm margin followed by reconstruction of the defect in the anterior abdominal wall either with local musculoaponeurotic layers or with synthetic mesh. In intra-abdominal cases associated with FAP in addition to surgery, hormonal treatment, chemotherapy and Radiotherapy are also advised depending upon the particular condition but usually prognosis is not encouraging. In this article we present our personal experience in the successful treatment of six cases of sporadic desmoids, five in females of child bearing age, and all in the anterior abdominal wall and one extra abdominal in a child aged 13 y in the gluteal region (Case 6). It is very interesting and unique to see two desmoid tumours developing in the same patient (Case2)one in each of the Rectus abdominal muscles (Right & Left).

Recurrent mutations within the amino-terminal region of β-catenin are probable key molecular driver events in sinonasal hemangiopericytoma

Sinonasal hemangiopericytoma (SN-HPC) is an uncommon, site-specific, low-grade mesenchymal neoplasm of probable perivascular myoid cell origin. In contrast to solitary fibrous tumors of soft tissue and sinonasal tract origin, SN-HPCs were recently shown to lack recurrent NAB2-STAT6 fusion variants. Other molecular alterations known to occur in some of soft tissue perivascular myoid cell neoplasms were also absent in SN-HPC; thus, the molecular pathogenesis of SN-HPCs remained unknown. Guided by whole-genome sequencing combined with RNA sequencing of an index case, we analyzed a total of six SN-HPCs for mutations within the amino-terminal region of the gene CTNNB1 (cadherin-associated protein), β 1, 88 kDa, encoding β-catenin. All six cases showed missense mutations, with amino acid substitutions clustering at positions 33 to 45, corresponding to the recognition site of the β-catenin destruction complex. Similar CTNNB1 mutations have been described in a variety of epithelial and mesenchymal neoplasms. These mutations prevent β-catenin phosphorylation and proteasomal degradation but promote its nuclear accumulation and subsequent increased transcription of Wingless-related integration site target genes. Consistent with these molecular findings, β-catenin IHC showed consistent diffuse and strong nuclear staining of the tumor cells in all six SN-HPCs. Our results highlight, for the first time, CTNNB1 mutations as the likely initiating molecular events driving SN-HPC tumorigenesis, which places SN-HPC among the growing family of β-catenin-driven mesenchymal neoplasms.

Prognostic value of CTNNB1 gene mutation in primary sporadic aggressive fibromatosis

BACKGROUND

Aggressive fibromatosis (AF) comprises tumors with a varying biological behavior. Genetic tumor characteristics may be predictive of recurrence; hence, the prognostic value of three specific mutations on the CTNNB1 gene was evaluated in relation to known clinicopathologic risk factors in patients with primary, sporadic AF.

METHODS

In a multi-institutional retrospective cohort study of patients with primary extra-abdominal and abdominal wall AF who underwent surgical treatment, the original pathology specimens were reviewed for the presence of a T41A, S45F, and 45P mutations on the CTNNB1 gene. For these mutations, the risk of recurrence was analyzed by the Kaplan-Meier method with log-rank test. Univariable and multivariable Cox regression was performed to calculate hazard ratios.

RESULTS

A total of 101 patients were analyzed. During a median follow-up of 41 months, 17 recurrences were detected; the cumulative 5-year recurrence rate was 22.8 %. A specific CTNNB1 mutation was found in 76 patients, with the majority of patients having a T41A mutation (n = 49). CTNNB1 mutations were associated with the risk of recurrence: the presence of a S45F mutation was associated with a 5-year cumulative risk of recurrence of 63.8 % (P < 0.001). Multivariable analysis showed that young age and S45F mutation were independent risk factors (P = 0.011 and P < 0.001).

CONCLUSIONS

The presence of specific CTNNB1 mutations was predictive for recurrence in patients after surgical treatment for primary, sporadic extra-abdominal and abdominal AF. A S45F mutation increased the risk of recurrence significantly.

Isolated limb perfusion using tumour necrosis factor α and melphalan in patients with advanced aggressive fibromatosis

Background

Aggressive fibromatoses (desmoid tumours) may be locally aggressive, but do not metastasize. Although a conservative approach is advocated for most patients, pain and functional impairment are indications for active treatment. Tumour necrosis factor (TNF) α and melphalan-based isolated limb perfusion (TM-ILP) is a limb-saving treatment modality for soft tissue tumours. This study reports the results of TM-ILP treatment in patients with aggressive fibromatosis.

Methods

Institutional databases of three European centres were searched. All patients who received TM-ILP treatment for aggressive fibromatosis between 1990 and 2012 were included. Before therapy, the patients were discussed at multidisciplinary tumour board meetings.

Results

Twenty-five patients received 28 TM-ILP treatments. The median age of patients was 28 (i.q.r. 19–34) years and median hospital stay was 8 (7–12) days. Median follow-up was 84 (34–114) months. A complete response was achieved after two TM-ILP treatments, and a partial response after 17 treatments in 16 patients. Stable disease was reported after eight treatments in seven patients, including a patient with stable disease after the first treatment and progression after the second TM-ILP. Toxicity was modest after most treatments; Wieberdink grade IV (extensive epidermolysis, and threatening or manifest compartment syndrome) was seen after two TM-ILP treatments. Systemic leakage was reported after one treatment, but did not lead to systemic toxicity. Functional outcome was good; 16 patients had no physical limitations, and six patients had some limitations but did not need medical aids. Amputation was prevented in all but three patients.

Conclusion

TNF-α-based ILP is effective in patients with aggressive fibromatosis.

Identification of previously unrecognized FAP in children with Gardner fibroma

Fibromatous soft tissue lesions, namely desmoid-type fibromatosis and Gardner fibroma, may occur sporadically or as a result of inherited predisposition (as part of familial adenomatous polyposis, FAP). Whereas desmoid-type fibromatosis often present β-catenin overexpression (by activating CTNNB1 somatic variants or APC biallelic inactivation), the pathogenetic mechanisms in Gardner fibroma are unknown. We characterized in detail Gardner fibromas diagnosed in two infants to evaluate their role as sentinel lesions of previously unrecognized FAP. In the first infant we found a 5q deletion including APC in the tumor and the novel APC variant c.4687dup in constitutional DNA. In the second infant we found the c.5826_5829del and c.1678A>T APC variants in constitutional and tumor DNA, respectively. None of the constitutional APC variants occurred de novo and both tumors showed nuclear staining for β-catenin and no CTNNB1 variants. We present the first comprehensive characterization of the pathogenetic mechanisms of Gardner fibroma, which may be a sentinel lesion of previously unrecognized FAP families.

Targeting stem cell behavior in desmoid tumors (aggressive fibromatosis) by inhibiting hedgehog signaling

Desmoid tumor (also called aggressive fibromatosis) is a lesion of mesenchymal origin that can occur as a sporadic tumor or a manifestation of the preneoplastic syndrome, familial adenomatous polyposis caused by a mutation in adenomatous polyposis coli (APC). This tumor type is characterized by the stabilization of β-catenin and activation of Tcf-mediated transcription. Cell transplantation data suggest that desmoid tumors are derived from mesenchymal progenitor cells (MSCs). As such, modulating cell signaling pathways that regulate MSC differentiation or proliferation, such as hedgehog (Hh) signaling, could alter the tumor phenotype. Here, we found that Hh signaling is activated in human and murine desmoid tumors. Inhibiting Hh signaling in human cell cultures decreased cell proliferation and β-catenin protein levels. Apc(+)/Apc(1638N) mice, which develop desmoid tumors, develop smaller and fewer tumors when Hh signaling was inhibited either genetically (by crossing Apc(+)/Apc(1638N) mice with mice lacking one copy of a Hh-activated transcription factor, Gli2 (+/-) mice) or using a pharmacologic inhibitor. Both in mice and in human tumor cell cultures, β-catenin and Hh-mediated signaling positively regulate each other's activity. These data show that targeting a pathway that regulates MSC differentiation influences desmoid tumor behavior, providing functional evidence supporting the notion that these tumors are derived from mesenchymal progenitors. It also suggests Hh blockade as a therapeutic approach for this tumor type.

Desmoid tumors of the head and neck: a therapeutic challenge

Desmoid tumor, or aggressive fibromatosis, is a rare, histologically benign, fibroblastic lesion that infrequently presents in the head and neck. Desmoid tumors often grow locally, invasively, and may, in rare instances, be fatal secondary to invasion into critical structures, such as airway or major vessels. The most common treatment is surgery, but desmoid tumors are characteristically associated with a high local recurrence rate after resection. Although the margin status seems to be of importance, operations that avoid function loss and esthetic disfigurement should be the primary goal. The efficacy of postoperative radiotherapy is controversial. Its potential benefit should be carefully balanced against possible radiation-induced adverse effects. Alternative treatment modalities, such as primary radiotherapy and medical treatment or a wait-and-see policy, may be preferable to mutilating surgery. Considering all the aforementioned, it seems obvious that desmoid tumors of the head and neck present a therapeutic challenge and require an individualized approach.

Desmoid-type fibromatosis of the head and neck region in the paediatric population: a clinicopathological and genetic study of seven cases

AIMS

Desmoid-type fibromatosis (desmoid) is a locally aggressive (myo)fibroblastic lesion. It represents one of the more common fibrous tumours in children and adolescents. The head and neck region is more often involved than in adults.

METHODS AND RESULTS

We investigated the clinicopathological and genetic characteristics of seven paediatric desmoids at this anatomical site, including two cases of desmoplastic fibroma located in the mandible. There were two females and five males with an age range of 1.5-8 years. The sites of the soft tissue lesions were sinonasal (n = 4) and paramandibular (n = 1). All cases showed typical morphology and nuclear β-catenin expression. CTNNB1 gene sequencing, performed successfully in five cases, revealed mutations in three cases with one p.T41A (bone lesion), one p.S37A and one novel mutation, p.D32V (sinonasal soft tissue lesions). Six patients were treated by excision with positive margins in five cases. Follow-up, available for six patients (median 4 years), showed no evidence of disease in four cases, slow progression in one case, and recurrence with stable disease in the last case.

CONCLUSIONS

Our study provides evidence of genetic similarities in desmoid and desmoplastic fibroma. Additionally, we expanded the spectrum of mutations in CTNNB1 with one novel desmoid mutation.

A prognostic nomogram for prediction of recurrence in desmoid fibromatosis

OBJECTIVE

To construct a postoperative nomogram to estimate the risk of local recurrence for patients with desmoid tumors.

BACKGROUND

The standard management of desmoid tumors is resection, but many recur locally. Other options include observation or novel chemotherapeutics, but little guidance exists on selecting treatment.

METHODS

Patients undergoing resection during 1982-2011 for primary or locally recurrent desmoids were identified from a single-institution prospective database. Cox regression analysis was used to assess risk factors and to create a recurrence nomogram, which was validated using an international, multi-institutional data set.

RESULTS

Desmoids were treated surgically in 495 patients (median follow-up of 60 months). Of 439 patients undergoing complete gross resection, 100 (23%) had recurrence. Five-year local recurrence-free survival was 69%. Eight patients died of disease, all after R2 resection. Adjuvant radiation was not associated with improved local recurrence-free survival. In multivariate analysis, factors associated with recurrence were extremity location, young age, and large tumor size, but not margin. Abdominal wall tumors had the best outcome (5-year local recurrence-free survival rate of 91%). Age, site, and size were used to construct a nomogram with concordance index of 0.703 in internal validation and 0.659 in external validation. Integration of additional variables (R1 margin, sex, depth, and primary vs recurrent presentation) did not importantly improve concordance (internal concordance index of 0.707).

CONCLUSIONS

A postoperative nomogram including only size, site, and age predicts local recurrence and can aid in counseling patients. Systemic therapies may be appropriate for young patients with large, extremity desmoids, but surgery alone is curative for most abdominal wall lesions.

Intra-abdominal desmoid tumor difficult to distinguish from a gastrointestinal stromal tumor: report of two cases

Desmoid tumors are benign fibroblastic neoplasms with no metastatic potential, but a propensity for local recurrence even after complete surgical resection. These lesions can develop at any site in the body, and commonly occur in the intra-abdominal area. Intra-abdominal desmoid tumors usually occur at the mesentery or retroperitoneum, and may morphologically mimic gastrointestinal stromal tumors (GISTs). Distinguishing between these tumors is important, because the therapies differ substantially, but is often difficult even with the use of CD117 staining. We herein report the cases of two patients with sporadic intra-abdominal desmoid tumors that were differentiated from GIST by immunohistological examination using beta-catenin and CD34. Desmoid tumors specifically express nuclear beta-catenin, and show no expression of CD34. We recommend staining for beta-catenin and CD34 when an intra-abdominal desmoid tumor is suspected.

β-Catenin mutation status and outcomes in sporadic desmoid tumors

BACKGROUND

Mutations in the gene-encoding β-catenin, CTNNB1, are highly prevalent in sporadic desmoid tumors and may predict the risk for recurrence. We sought to determine the prevalence of CTNNB1 mutations in a large cohort of sporadic desmoid tumors and to determine whether CTNNB1 mutation status correlates with disease outcome.

METHODS

Single-base extension genotyping of the CTNNB1 gene was performed on 145 sporadic, paraffin-embedded desmoid tumor specimens. Correlation of mutation status with outcome was performed on a subset of 115 patients who underwent macroscopically complete surgical resection.

RESULTS

CTNNB1 mutations were detected in 106 of 145 (73%) tumor specimens and in 86 of 115 (75%) specimens from patients who underwent curative-intent surgical resection, including discrete mutations in the following codons of CTNNB1 exon 3: T41A (46%), S45F (25%), S45P (1.7%), and S45C (0.9%). Desmoid tumors of the superficial trunk were significantly less likely to harbor CTNNB1 mutations than tumors located elsewhere, but none of the other examined clinicopathologic factors were found to be associated with CTNNB1 mutation status. At a median follow-up of 31 months, 5-year recurrence-free survival was slightly, although not statistically significantly, worse for patients with β-catenin-mutated tumors than for those with wild-type tumors (58% vs. 74%, respectively). The specific CTNNB1 codon mutation did not correlate with the risk for recurrence.

CONCLUSION

CTNNB1 mutations are indeed common in sporadic desmoid tumors. However, our study did not detect a statistically significant difference in recurrence risk according to either the CTNNB1 mutation status or the specific CTNNB1 mutation.

Surgical outcome of desmoid tumors: adjuvant radiotherapy delayed the recurrence, but did not affect long-term outcomes

BACKGROUND

We retrospectively reviewed the outcomes of desmoid tumor (DT) patients treated by surgical excision.

METHODS

Among 155 consecutive patients, 119 patients satisfied our inclusion criteria. The mean follow-up duration was 82 months. Age, gender, location, size, depth, resection margin, adjuvant radiotherapy, and excision history were analyzed for the outcomes.

RESULTS

The recurrence-free survival (RFS) rates were 75% at 5 years and 72% at 10 years. Twenty-seven (93.1%) out of 29 recurrences were detected within 5 years. In multivariate analysis, positive resection margin and excision history were independently associated with the RFS. In the comparison between the propensity score matched groups, adjuvant radiotherapy was not significantly associated with the RFS. The mean time interval from surgery to recurrence was 30.0 ± 28.7 months (median, 20 months; range, 4-123 months). This interval was significantly longer for patients who received adjuvant radiotherapy than for those who received surgical resection only, both in all recurrences and in recurrences in matched cases.

CONCLUSIONS

Surgical excision appears to be a reliable treatment option for DTs. However, positive outcomes require a clear resection margin. Adjuvant radiotherapy may delay the recurrence of the tumor, although it seems to have no effect on the ultimate relapse rate.

Nuclear GSK-3β segregation in desmoid-type fibromatosis

AIMS

Desmoid-type fibromatosis (DF) is a rare benign myofibroblastic neoplasm of the connective tissue that is unable to metastasize but is associated with a high local recurrence rate. Nuclear β-catenin is the most commonly used histological marker of DF; however, clinical and biological predictive markers guiding the treatment and follow-up of DF are still lacking. Normally, β-catenin is regulated by the cytoplasmic multiprotein complex of adenomatous polyposis coli (APC), axin, casein kinase 1α (CK1α), and glycogen synthase kinase 3β (GSK-3β); this phosphorylates and degrades β-catenin, which would otherwise translocate to the nucleus. The aim of this study was to analyse the expression and localization of the β-catenin-protein complex of the Wnt pathway in cells isolated from DF patients.

METHODS AND RESULTS

We isolated cells from biopsies of DF patients, and demonstrated, by immunofluorescence and immunoblot analyses, that it is almost exclusively nuclear GSK-3β that colocalizes and interacts with β-catenin. The nuclear translocation of β-catenin and GSK-3β is not correlated with CTNNB1 mutations. In DF samples, the multiprotein complex is disrupted, as the cytoplasmic localization of APC and axin makes interaction with the nuclear β-catenin and GSK-3β impossible.

CONCLUSIONS

Our data suggest that GSK-3β is an additional DF marker with an important role in the aetiopathogenesis of this entity.

Successful outcome after laparoscopic surgery for sporadic colonic desmoid tumor with β-catenin mutation: a case report

Introduction

Desmoid tumors (also called aggressive fibromatosis) are histologically benign, but have a strong tendency to recur locally after resection. They are rare neoplastic tumors that may occur sporadically or in association with familial adenomatous polyposis caused by a germline mutation in the adenomatous polyposis coli gene. The etiology of desmoid tumors is unknown, but their association with a history of abdominal surgery, trauma, and estrogen therapy is well known.

Case presentation

A 36-year-old Asian woman was referred complaining of an abdominal tumor. She had no history of familial adenomatous polyposis, abdominal surgery, trauma or pregnancy. A laparoscopy-assisted right hemicolectomy with a minilaparotomy was conducted for resection of her right-side colon and the anterior wall of her duodenum. The histopathological diagnosis was a desmoid tumor that grew from the transverse mesocolon. Mutational analysis indicated a mutation of the β-catenin gene (CTNNB1), consisting of a substitution of threonine for alanine at codon 41. The patient has been followed postoperatively for more than 3 years without any sign of recurrence.

Conclusion

We report a case of sporadic colonic desmoid tumor which was resected by laparoscopic surgery. A successful outcome was achieved because there has been no local recurrence for more than 3 years. The tumor grew from the transverse mesocolon, and harbored a mutation of the CTNNB1 gene. Mutational analysis of CTNNB1 gene may play an important role as a prognostic marker of desmoid tumors.

CTNNB1 mutation analysis is a useful tool for the diagnosis of desmoid tumors: a study of 260 desmoid tumors and 191 potential morphologic mimics

Desmoid tumors are benign monoclonal fibroblastic or myofibroblastic neoplasms, characterized by local invasiveness and high rates of recurrence. Desmoid tumors must be distinguished from benign fibroblastic and myofibroblastic lesions, as well as from low-grade sarcoma, which can appear histologically similar to desmoid tumors. This differential diagnosis can be very difficult, especially when diagnosis is based on a core needle biopsy. On the molecular level, most sporadic desmoid tumors are associated with mutations of the β-catenin gene (CTNNB1). A minority of desmoid tumors are associated with Gardner syndrome and mutations of the familial adenomatous polyposis gene. We identified the common CTNNB1 mutations associated with sporadic desmoid tumors by direct sequencing: in (i) 260 cases of typical desmoid tumors; and (ii) in 191 cases of spindle cell lesions, which can morphologically 'mimic' desmoid tumors. Formalin-fixed paraffin-embedded tissues were obtained via core needle biopsy (n=150) or open biopsy/surgical excision (n=301). Only 16 cases (4%) were not analyzable (Bouin's fixed tissue). CTNNB1 mutations were observed in 223 of 254 (88%) of sporadic desmoid tumors. No CTNNB1 mutations were detected in all other lesions (n=175) studied. CTNNB1 sequencing can be easily and reliably done using tissues obtained via core needle biopsy. Detection of CTNNB1 mutations in formalin-fixed paraffin-embedded tissues among spindle cell lesions is proposed as a specific diagnostic tool for the diagnosis of desmoid tumors. This result has significant implications for patient care and management.