Detection of beta-catenin mutations in paraffin-embedded sporadic desmoid-type fibromatosis by mutation-specific restriction enzyme digestion (MSRED): an ancillary diagnostic tool

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Does the Addition of Mutations of CTNNB1 S45F to Clinical Factors Allow Prediction of Local Recurrence in Patients With a Desmoid Tumor? A Local Recurrence Risk Model

BACKGROUND

The initial approach to the treatment of desmoid tumors has changed from surgical resection to watchful waiting. However, surgery is still sometimes considered for some patients, and it is likely that a few patients would benefit from tumor removal if the likelihood of local recurrence could be predicted. However, to our knowledge, there is no tool that can provide guidance on this for clinicians at the point of care.

QUESTION/PURPOSE

We sought to explore whether a combined molecular and clinical prognostic model for relapse in patients with desmoid tumors treated with surgery would allow us to identify patients who might do well with surgical excision.

METHODS

This was a retrospective, single-center study of 107 patients with desmoid tumors who were surgically treated between January 1980 and December 2015, with a median follow-up of 106 months (range 7 to 337 months). We correlated clinical variables (age, tumor size, and localization) and CTNNB1 gene mutations with recurrence-free survival. Recurrence-free survival was estimated using a Kaplan-Meier curve. Univariate and multivariable analyses of time to local recurrence were performed using Cox regression models. A final nomogram model was constructed according to the final fitted Cox model. The predictive performance of the model was evaluated using measures of calibration and discrimination: calibration plot and the Harrell C-statistic, also known as the concordance index, in which values near 0.5 represent a random prediction and values near 1 represent the best model predictions.

RESULTS

The multivariable analysis showed that S45F mutations (hazard ratio 5.25 [95% confidence interval 2.27 to 12.15]; p < 0.001) and tumor in the extremities (HR 3.15 [95% CI 1.35 to 7.33]; p = 0.008) were associated with a higher risk of local recurrence. Based on these risk factors, we created a model; we observed that patients considered to be at high risk of local recurrence as defined by having one or two factors associated with recurrence (extremity tumors and S45F mutation) had an HR of 8.4 compared with patients who had no such factors (95% CI 2.84 to 24.6; p < 0.001). From these data and based on the multivariable Cox models, we also developed a nomogram to estimate the individual risk of relapse after surgical resection. The model had a concordance index of 0.75, or moderate discrimination.

CONCLUSION

CTNNB1 S45F mutations combined with other clinical variables are a potential prognostic biomarker associated with the risk of relapse in patients with desmoid tumors. The developed nomogram is simple to use and, if validated, could be incorporated into clinical practice to identify patients at high risk of relapse among patients opting for surgical excision and thus help clinicians and patients in decision-making. A large multicenter study is necessary to validate our model and explore its applicability.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Case Report: Desmoid tumor response to magnetic resonance-guided high intensity focused ultrasound over 4 years

Desmoid tumors are a rare form of cancer, which show locally aggressive invasion of surrounding tissues and may occur anywhere in the body. Treatment options comprise conservative watch and wait strategies as tumors may show spontaneous regression as well as surgical resection, radiation therapy, nonsteroidal anti-inflammatory drugs (NSAID), chemotherapy, or local thermoablative approaches for progressive disease. The latter comprises cryotherapy, radiofrequency, microwave ablation, or thermal ablation with high intensity focused ultrasound (HIFU) as the only entirely non-invasive option. This report presents a case where a desmoid tumor at the left dorsal humerus was 2 times surgically resected and, after recurrence, thermally ablated with HIFU under magnetic resonance image-guidance (MR-HIFU). In our report, we analyze tumor volume and/or pain score during standard of care (2 years) and after HIFU treatment over a 4-year follow-up period. Results showed MR-HIFU treatment led to complete tumor remission and pain response.

The Recent Advances in Molecular Diagnosis of Soft Tissue Tumors

Soft tissue tumors are rare mesenchymal tumors with divergent differentiation. The diagnosis of soft tissue tumors is challenging for pathologists owing to the diversity of tumor types and histological overlap among the tumor entities. Present-day understanding of the molecular pathogenesis of soft tissue tumors has rapidly increased with the development of molecular genetic techniques (e.g., next-generation sequencing). Additionally, immunohistochemical markers that serve as surrogate markers for recurrent translocations in soft tissue tumors have been developed. This review aims to provide an update on recently described molecular findings and relevant novel immunohistochemical markers in selected soft tissue tumors.

Droplet Digital PCR (ddPCR) as a Novel Technology in Detecting CTNNB1 Mutations in Desmoid Fibromatosis

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.

Low to Intermediate (Borderline) Grade Breast Spindle Cell Lesions on Needle Biopsy: Diagnostic Approach and Clinical Management

Spindle cell proliferations of the breast are a heterogeneous group of lesions ranging from benign or reactive lesions to aggressive malignant neoplasms. Diagnosis on core biopsy can be particularly challenging as lesions displaying different lineages associated with variable outcomes share overlapping morphologies (scar vs. fibromatosis-like metaplastic carcinoma) whereas individual entities can exhibit a large variety of appearances (myofibroblastoma). In this review, lesions are grouped into lineage, when possible, including those showing fibroblastic/myofibroblastic differentiation, ranging from entities that require no additional management, such as scar and nodular fasciitis, to those with unpredictable clinical outcomes such as fibromatosis and solitary fibrous tumor or locally aggressive behavior such as dermatofibrosarcoma protuberans. The review of low-grade vascular lesions includes atypical vascular lesion and low-grade angiosarcoma. Also discussed are various adipocytic lesions ranging from lipoma to liposarcoma, and rare smooth muscle and neural entities more commonly encountered in locations outside the breast, such as leiomyoma, neurofibroma, schwannoma, or granular cell tumor. Optimal histological evaluation of these entities merges clinical and radiologic data with morphology and ancillary testing. We present our approach to immunohistochemical and other ancillary testing and highlight issues in pathology correlation with imaging. Recent updates in the management of breast spindle cell lesions are addressed. In a well-sampled lesion with radiographic concordance, the core biopsy diagnosis reliably guides management and we advocate the inclusion of management recommendations in the pathology report. Precise characterization using up to date guidelines is important to identify a subset of patients who may safely avoid unnecessary surgical procedures. A multidisciplinary approach with close collaboration with our clinical colleagues is emphasized.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Soft Tissue Tumors

The fifth (5th) edition of the World Health Organization (WHO) Classification of Head and Neck Tumors introduces a new chapter dedicated to soft tissue neoplasms commonly affecting the head and neck. While the diversity, rarity, and wide anatomic range of soft tissue tumors precludes a discussion of all entities that may be found in the head and neck, the addition of this new chapter to the head and neck "blue book" aims to provide a more comprehensive and uniform reference text, including updated diagnostic criteria, of mesenchymal tumor types frequently (or exclusively) arising at head and neck sites. Since publication of the previous edition in 2017, there have been numerous advances in our understanding of the pathogenesis of many soft tissue tumors which have facilitated refinements in tumor classification, identification of novel entities, development of diagnostic markers, and improved prognostication. This review will provide a focused discussion of the soft tissue tumors included in the 5th edition WHO Head and Neck classification, with an emphasis on updates.

Recurrent CTNNB1 mutations in craniofacial osteomas

Osteoma is a benign bone forming tumor predominantly arising on the surface of craniofacial bones. While the vast majority of osteomas develops sporadically, a small subset of cases is associated with Gardner syndrome, a phenotypic variant of familial adenomatous polyposis caused by mutations in the APC gene resulting in aberrant activation of WNT/β-catenin signaling. In a sequencing analysis on a cohort of sporadic, non-syndromal osteomas, we identified hotspot mutations in the CTNNB1 gene (encoding β-catenin) in 22 of 36 cases (61.1%), harbouring allelic frequencies ranging from 0.04 to 0.53, with the known S45P variant representing the most frequent alteration. Based on NanoString multiplex expression profiling performed in a subset of cases, CTNNB1-mutated osteomas segregated in a defined "WNT-cluster", substantiating functionality of CTNNB1 mutations which are associated with β-catenin stabilization. Our findings for the first time convincingly show that osteomas represent genetically-driven neoplasms and provide evidence that aberrant WNT/β-catenin signaling plays a fundamental role in their pathogenesis, in line with the well-known function of WNT/β-catenin in osteogenesis. Our study contributes to a better understanding of the molecular pathogenesis underlying osteoma development and establishes a helpful diagnostic molecular marker for morphologically challenging cases.

Spindle Cell Tumors of the Pleura and the Peritoneum: Pathologic Diagnosis and Updates

A diverse group of both benign and malignant spindle cell tumors can involve the pleura or the peritoneum. Due to their rarity and overlapping morphologic features, these tumors can pose considerable diagnostic difficulty in surgical pathology. As these tumors differ in their prognosis and clinical management, their correct pathologic diagnosis is critical. In addition to histologic assessment, select immunohistochemical and molecular tools can aid the distinction among these tumors. In this review, we consider some of the major histologic differential diagnosis of spindle cell tumors involving these serosal membranes. This list of tumors includes: solitary fibrous tumor, inflammatory myofibroblastic tumor, desmoid fibromatosis, synovial sarcoma, sarcomatoid carcinoma, spindle cell melanoma, dedifferentiated liposarcoma, epithelioid hemangioendothelioma, and sarcomatoid mesothelioma. We describe their salient clinicopathologic and genetic findings, with a review on some of the recent discoveries on their molecular pathogenesis.

Neuromuscular Choristoma: Report of Five Cases With CTNNB1 Sequencing

Neuromuscular choristoma (NMC) are lesions of the peripheral nervous system characterized by an admixture of skeletal muscle fibers and nerves fascicles that are frequently associated with desmoid fibromatosis (DF). Mutations in CTNNB1, the gene for β-catenin protein, are common in DF and related to its pathogenesis. They are restricted to exon 3, with 3 point mutations: T41A, S45F, and S45P. To understand the pathogenesis of NMC, we tested CTNNB1 status in 5 cases of NMC whether or not they were associated with DF. The screening of mutations in CTNNB1 gene was based on amplicon deep sequencing using the ION Proton platform. Three patients had the S45F mutation; in 2 the mutation was common to both lesions and in one the DF was wild type while the NMC had the S45F mutation. One patient had a T41A mutation in the NMC and no associated DF. In the last patient, the DF lesion had a T41A mutation; there was no lesion with the S45P mutation. The presence of similar CTNNB1 mutations in NMC/DF-associated lesions and sporadic DF reinforces the relationship between both lesions and points to a common pathogenic mechanism.

Molecular Alterations in Pediatric Fibroblastic/Myofibroblastic Tumors: An Appraisal of a Next Generation Sequencing Assay in a Retrospective Single Centre Study

BACKGROUND

Pediatric fibroblastic/myofibroblastic tumors (PFMTs) can be challenging to definitively classify. Large case series or diagnostic updates have not been recently published despite identification of molecular alterations that could improve diagnostic accuracy. Our review of the literature found that over two-thirds of the more than 30 types of PFMTs harbor recurrent molecular alterations. We performed an institutional review of PFMTs to highlight limitations of a predominantly morphological classification, and evaluated the utility of a next-generation sequencing assay to aid diagnosis.

METHODS

PFMTs identified over a period of 12 years were reviewed, categorized per the new WHO classification, and tested using the Oncomine Childhood Cancer Research Assay.

RESULTS

Eighty-seven specimens from 58 patients were reviewed; 50 were chosen for molecular analysis, 16 (32%) lacking definitive classification. We identified alterations, some novel, in 33% of assayed cases. Expected alterations were identified for most known diagnoses and mutations were identified in 6 of 16 tumors (38%) that were initially unclassified.

CONCLUSION

We confirmed a significant subset of PFMTs remain difficult to classify using current criteria, and that a combined DNA/RNA assay can identify alterations in many of these cases, improving diagnostic certainty and suggesting a clinical utility for challenging cases.

Cutaneous desmoid-type fibromatosis: A rare case with molecular profiling

Fibromatoses encompass a broad group of histopathologically similar fibroblastic/myofibroblastic proliferations with divergent clinical manifestations and behavior. Deep (desmoid-type) fibromatoses are typically large, rapidly growing, and locally aggressive tumors that occur in the abdominal wall, mesentery, and extra-abdominal soft tissue, principally the musculature of the trunk and extremities. Most sporadic cases of desmoid fibromatosis harbor inactivating mutations in CTNNB1, the gene encoding beta-catenin. Tumors occurring in the context of familial adenomatous polyposis and Gardner syndrome bear inactivating mutations in APC. By contrast, mutations in CTNNB1 or APC have not been identified in cases of superficial fibromatosis. Cutaneous involvement by desmoid fibromatosis is exceedingly rare. Here we present a 78-year-old male with desmoid-type fibromatosis arising in the dermis of the right medial calf with a pathogenic mutation in CTNNB1 and a variant of unknown significance in APC.

Clinicopathological features of 70 desmoid-type fibromatoses confirmed by β-catenin immunohistochemical staining and CTNNB1 mutation analysis

Desmoid-type fibromatosis (DF) is a locally aggressive neoplasm characterized by mutations in the CTNNB1 gene, which encodes the β-catenin protein. We reviewed 85 cases of DF and performed Sanger sequencing for detecting mutations in CTNNB1 and immunostaining for detecting β-catenin localization. We included 70 DF samples, of which 56 cases demonstrated nuclear β-catenin localization and 43 cases harboured CTNNB1 mutations. CTNNB1-mutant DF samples consistently displayed nuclear β-catenin expression and were derived from larger-sized tumours compared to samples with wild-type CTNNB1. When we further classified DF cases into 2 subgroups based on the type of specimen, excised specimens with nuclear β-catenin expression frequently displayed CTNNB1 mutation and no statistical correlation between nuclear β-catenin expression and CTNNB1 mutation was observed in biopsies. When we classified CTNNB1 mutation cases into 2 subgroups (DF with T41A or T41I, and DF with S45F or S45P), T41A or T41I mutations were observed more frequently in males than in females. Additionally, DF tumours harbouring S45F or S45P mutations were located more frequently in the abdominal wall than tumours with T41A or T41I mutations. In conclusion, CTNNB1 mutation correlates with nuclear β-catenin expression in larger or excised DF tumours, and DF harbouring CTNNB1 mutations manifest variable clinical presentations.

A Rare Incident of Intraarticular Fibromatosis of the Knee: A Case Report

CASE

Our patient is a 34-year-old male aHthlete who presented for consultation after left knee discomfort and pressure for greater than 2 years. Advanced imaging revealed a nonspecific intraarticular suprapatellar lesion with subsequent ultrasound-guided core biopsy demonstrating a spindle cell proliferation consistent with superficial fibromatosis. Thus, the patient underwent an open en bloc surgical resection by a fellowship-trained orthopaedic oncologist.

CONCLUSION

As the first reported case of intraarticular fibromatosis of the knee, this case highlights the importance of a thoughtful approach to the management of nonspecific intraarticular lesions through a comprehensive and collaborative strategy to decrease patient morbidity and optimize outcomes.

Management of aggressive fibromatosis

Aggressive fibromatosis or desmoid tumor is a rare disease resulting from fibroblasts which do not metastasize. However, desmoid tumors belong to low-grade malignant tumors since they have high potential to infiltrate surrounding tissues, causing high local recurrence rates and may affect surrounding organs, threatening life quality and expectancy. Although surgery, watch and wait, radiotherapy, chemotherapy, high intensity focused ultrasound, ablation techniques or several agents have all been frequently investigated for the treatment of this type of disease, none are deemed as standard therapy for high recurrence rates that have been supported by any data. The present review retrieved literature on treatment options for desmoids to summarize the latest treatment modalities and refine their efficacy, as well as their side effects, in order to provide a more comprehensive treatment reference for clinicians.

Is mutation analysis of β-catenin useful for the diagnosis of desmoid-type fibromatosis? A systematic review

BACKGROUND

An accurate diagnosis is crucial to determine the treatment modality for desmoid-type fibromatosis, although the histopathological diagnosis is occasionally difficult to make. Many desmoid-type fibromatosis have been reported to have hotspot mutation of β-catenin gene (CTNNB1). In the present study, we performed a systematic review to verify the usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis.

METHODS

A literature search from January 1990 to August 2017 was conducted. Three reviewers independently assessed and screened the literature for eligibility and determined the final articles to be evaluated. Data regarding the sensitivity, specificity, accuracy and usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis were recorded. We rated each report according to the Grading of Recommendations Development and Evaluation approach.

RESULTS

The search yielded 90 studies, seven of which were included after the first and second screenings. The positive rate of CTNNB1 mutation in desmoid-type fibromatosis was 86.8%, but the cohort of six of the seven reports was already diagnosed histopathologically as desmoid-type fibromatosis. Therefore, the usefulness of CTNNB1 mutation analysis in a cohort that is difficult to diagnose histopathologically is not clear in this review. Nevertheless, CTNNB1 mutation showed very high specificity in desmoid-type fibromatosis, indicating the usefulness of CTNNB1 mutation analysis in its diagnosis in combination with histological examination.

CONCLUSION

Because the lack of data precludes any useful comparison with histological diagnosis, the evidence level is low. However, considering its specificity, CTNNB1 mutation analysis may be useful in cases in which the histopathological diagnosis is difficult.

New Advances in Molecular Breast Cancer Pathology

Breast cancer (BC) comprises a diverse spectrum of diseases featuring distinct presentation, morphological, biological, and clinical phenotypes. BC behaviour and response to therapy also vary widely. Current evidence indicates that traditional prognostic and predictive classification systems are insufficient to reflect the biological and clinical heterogeneity of BC. Advancements in high-throughput molecular techniques and bioinformatics have contributed to the improved understanding of BC biology, refinement of molecular taxonomies and the development of novel prognostic and predictive molecular assays. Molecular testing has also become increasingly important in the diagnosis and treatment of BC in the era of precision medicine. Despite the enormous amount of research work to develop and refine BC molecular prognostic and predictive assays, it is still in evolution and proper incorporation of these molecular tests into clinical practice to guide patient's management remains a challenge. With the increasing use of more sophisticated high throughput molecular techniques, large amounts of data will continue to emerge, which could potentially lead to identification of novel therapeutic targets and allow more precise classification systems that can accurately predict outcome and response to therapy. In this review, we provide an update on the molecular classification of BC and molecular prognostic assays. Companion diagnostics, contribution of massive parallel sequencing and the use of liquid biopsy are also highlighted.

Novel pathogenic alterations in pediatric and adult desmoid-type fibromatosis - A systematic analysis of 204 cases

Desmoid-type fibromatosis (DTF, aggressive fibromatosis) is a non-metastasizing mesenchymal neoplasm of deep soft tissue with a tendency towards local recurrence. Genetic alterations affecting canonical Wnt/β-catenin signaling are reported in the majority of DTF. While most sporadic DTF harbor somatic mutations in CTNNB1, germline mutations in adenomatous polyposis coli (APC) are known to occur in hereditary DTF types (FAP, Gardner-Syndrome). Additional single nucleotide variants (SNVs) in AKT1 (E17K) and BRAF (V600E) were reported in pediatric DTF with potential clinical implications. We performed targeted next-generation sequencing (NGS) in a large cohort of 204 formalin-fixed DTF samples, comprising 22 pediatric cases (patients age ≤18 years). The mutational status was correlated with clinicopathological characteristics. Overall, deleterious CTNNB1 mutations were detected in 89% of DTF, most frequently affecting the serine/threonine phosphorylation sites T41 and S45 of β-catenin. While the T41A CTNNB1 mutation was significantly more often identified in the mesenterial localization, DTF originating from extra-intestinal sites more frequently harbored the S45P CTNNB1 alteration. Beyond common mutations in CTNNB1, additional SNVs were demonstrated in 7% of the DTF cohort and in 18% of the pediatric DTF subgroup. The mutational spectrum included deleterious mutations in AKT1 (G311S/D and T312I), ALK (R806H and G924S), AR (A159T), EGFR (P848L), ERBB2 (H174Y), IDH2 (H354Y), KIT (V559D), RET (T1038A), SDHA (R325M), and SDHD (R115W), as characterized by in silico prediction tools. In conclusion, our study indicates that DTF may harbor a broader mutational spectrum beyond CTNNB1 mutations, comprising targetable alterations including the herewith first reported imatinib-sensitive KIT V559D mutation in DTF.

An evidence-based guideline on the application of molecular testing in the diagnosis, prediction of prognosis, and selection of therapy in non-GIST soft tissue sarcomas

AIMS

To make recommendations on the indications for molecular testing regarding the diagnosis, prediction of prognosis, and treatment selection in adult patients with s oft tissue sarcomas (STS) excluding gastrointestinal stromal tumour.

MATERIALS AND METHODS

This guideline was developed by the Cancer Care Ontario's Program in Evidence-Based Care (PEBC) and the Sarcoma Disease Site Group (DSG). The medline, embase, and Cochrane Library databases, main guideline websites, abstracts of relevant annual meetings, and PROSPERO databases were searched (January 2005 to October 2016). Internal and external reviews were conducted, with final approval by the PEBC and the Sarcoma DSG.

RESULTS

Based on the available evidence, we made three S trong Recommendations, 14 Recommendations, 9 Qualified Statements, and seven No Recommendations. The three Strong Recommendations include: i) MDM2 amplification by fluorescence in situ hybridization (FISH) is recommended as a sensitive and specific test to differentiate patients with atypical lipomatous tumour/well-differentiated liposarcoma, or dedifferentiated liposarcoma from lipoma or other STS in the differential diagnosis; ii) SS18 (SYT) break-apart by FISH or SS18-SSX (SYT-SSX) fusion by reverse transcription-polymerase chain reaction is recommended as a sensitive and specific test to differentiate patients with synovial sarcoma from other sarcomas; iii) CTNNB1 S45F mutation by polymerase chain reaction is recommended as a prognostic factor for poor recurrence-free survival in patients with desmoid tumours.

CONCLUSION

This guideline may serve as a framework for the thoughtful implementation of molecular studies at cancer centres and other jurisdictions. Some of the recommendations may need to be updated when new evidence appears in the future.

Pediatric craniopharyngioma in association with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a cancer predisposition syndrome driven by germline loss-of-function of the APC gene and phenotypically manifests with intestinal polyposis and a variety of extra-intestinal bone and soft tissue tumors. Craniopharyngioma is not a well-described FAP-associated tumor, however, six cases have been reported in adults, all demonstrating ectopic location and adamantinomatous histology. We report the first case of craniopharyngioma associated with FAP in a pediatric patient. A seven-year-old girl who presented with headache and vomiting was found on magnetic resonance imaging to have a suprasellar mass with cystic extension to the pre-pontine space. The tumor represented an adamantinomatous craniopharyngioma (aCP) with nuclear β-catenin expression. Whole exome sequencing confirmed a CTNNB1 activating point mutation and a germline APC frameshift variant. This case represents the first FAP-associated craniopharyngioma in childhood…. expanding our understanding of the molecular underpinnings driving tumorigenesis in this unique patient.

Is immunohistochemical staining for β-catenin the definitive pathological diagnostic tool for desmoid-type fibromatosis? A multi-institutional study

Immunohistochemical staining with anti-β-catenin antibody has been applied as a diagnostic tool for desmoid-type fibromatoses (DFs). In recent years, specific gene mutation (CTNNB1) analysis has also been reported to be useful for diagnosis of DF; however, the association between CTNNB1 mutation status and immunohistochemical staining pattern of β-catenin is rarely reported. The purposes of this study are to clarify the relationship of the staining pattern of β-catenin with the CTNNB1 mutation status and various clinical variables, and to investigate the significance of immunohistochemical staining of β-catenin in cases diagnosed as DF. Between 1997 and 2017, 104 cases diagnosed as DF from 6 institutions in Japan were enrolled in this study: Nagoya University, National Cancer Center Hospital, Niigata University, Okayama University, Kyushu University, and Cancer Institute Hospital. For all cases, immunohistochemical staining of β-catenin and gene mutation analysis of CTNNB1 were performed. Of 104 cases, 87 (84%) showed nuclear staining of β-catenin, and 95 (91%) showed positive staining in the cytoplasm. The proportion of cases showing strong nuclear staining of β-catenin was significantly higher in the cases with S45F than in those with T41A or wild type. The proportion of cases stained strongly in the cytoplasm rather than in the nucleus was significantly higher in the group of T41A than that of S45F or wild type. Among 17 cases in which nuclear immunostaining was absent, CTNNB1 mutation was observed in 5 cases (29.4%). There were unignorable cases of DF with negative β-catenin immunostaining despite a definitive clinical and pathological diagnosis of DF and/or positive CTNNB1 mutation.

Proof of concept: prognostic value of the plasmatic concentration of circulating cell free DNA in desmoid tumors using ddPCR

Since desmoid tumors (DT) exhibit an unpredictable clinical course, with stabilization and/or spontaneous regression, an initial "wait-and-see" policy is the new standard of care-thus, the actual challenge is to identify early factors of progression. We present a method of detection of CTNNB1 mutations using a targeted digital droplet PCR (ddPCR) on cell-free DNA (cfDNA) extracted from blood samples of 31 DT patients. Furthermore, we analyzed the correlation between DT evolution and plasmatic concentration of total and mutated cfDNA at the time of diagnosis. Circulating copies of CTNNB1 mutants (ctDNA) were detected in the plasma of 6 patients (33%) but their concentration was not correlated with evolution of the tumor. Concentration of total cfDNA was higher in the plasma of patients with progressive desmoids (p = 0,0009). Using a threshold <900 copies/mL of plasma to detect indolent desmoid and a threshold >1375, it was possible to predict desmoid evolution for 65% of patients by measuring the quantity of circulating DNA in their plasma as early as the time of diagnosis. Albeit showing that the detection of CTNNB1 mutants is possible in the plasma of patients harboring a desmoid tumor, the results of this preliminary study raise the hypothesis that most of the circulating DNA detected in their plasma is derived from non-neoplastic cells, most likely normal neighboring tissues being actively invaded. Our results open the perspective of using cfDNA as a biomarker to predict prognosis at the time of diagnosis and assess tumor dynamics to optimize the treatment strategy.

Human microRNA expression in sporadic and FAP-associated desmoid tumors and correlation with beta-catenin mutations

Desmoid tumors (DT) are rare, benign, fibroblastic neoplasm with challenging histological diagnosis. DTs can occur sporadically or associated with the familial adenomatous polyposis coli (FAP). Most sporadic DTs are associated with β-catenin gene (CTNNB1) mutations, while mutated APC gene causes FAP disease. microRNAs (miRNAs) are involved in many human carcinogenesis.

The miRNA profile was analyzed by microarray in formalin-fixed, paraffin-embedded (FFPE) specimens of 12 patients (8 sporadic, 4 FAP-associated) and 4 healthy controls. One hundred and one mRNAs resulted dysregulated, of which 98 in sporadic DTs and 8 in FAP-associated DTs, 5 were shared by both tumors. Twenty-six miRNAs were then validated by RT-qPCR in 23 sporadic and 7 FAP-associated DT samples matched with healthy controls. The qPCR method was also used to evaluate the CTNNB1 mutational status in sporadic DTs. The correlation between sporadic DTs and miRNA expression showed that miR-21-3p increased in mutated versus wild-type DTs, while miR-197-3p was decreased. The mRNA expression of Tetraspanin3 and Serpin family A member 3, as miR-21-3p targets, and L1 Cell Adhesion Molecule, as miR-197-3p target, was also evaluate. CTNNB1 mutations associated to miRNA dysregulation could affect the genesis and the progression of this disease and help histological diagnosis of sporadic DTs.

Tumours composed of fat are no longer a simple diagnosis: an overview of fatty tumours with a spindle cell component

This is a review of the morphological spectrum of fatty tumours containing a component of spindle cells, highlighting the immunohistochemical and cytogenetic workup that is now mandatory for accurate diagnosis, with the goal of providing a practical approach for practising surgical pathologists. There have been significant advances in recent years in classifying and understanding the pathogenesis of fatty tumours with spindle cells, based on the correlation of histological, immunohistochemical and cytogenetic/molecular findings. In spite of this, morphological diagnosis and accurate classification of fatty tumours with spindle cells can be challenging to diagnostic pathologists. A group of three lesions: spindle cell lipoma, mammary-type myofibroblastoma and cellular angiofibroma share morphological features and are united by retinoblastoma protein (pRb) loss. Closely allied to these lesions, especially spindle cell lipoma is the newly designated atypical spindle cell lipomatous tumour, which shares morphological, immunohistochemical and cytogenetic features with the trio of tumours lacking nuclear pRb. All of these lesions lack MDM2 and CDK4 amplification as well and separation is based on clinical features, principally location. Atypical lipomatous tumour or well-differentiated liposarcoma shows retention of pRb but overexpression and amplification of MDM2. Fatty tumours with spindle cells need to be extensively sampled, with careful attention paid to cellular atypia and location, and they need to have immunohistochemical workup with pRb, MDM2, desmin, CD34 and p16. In addition, cytogenetic analysis for MDM2 and CDK4 amplification has become crucial for the proper identification of these lesions.

Desmoid-Type Fibromatosis: Who, When, and How to Treat

OPINION STATEMENT

Desmoid-type fibromatosis is a sarcoma subtype that gathers some singular characteristics, making it a difficult challenge to face in clinical practice. Despite its excellent survival prognosis, these tumors may be unpredictable, ranging from an asymptomatic indolent course to persistent, local, and extended recurrences that significantly impair quality of life. Although surgery was initially considered the first elective treatment, collected published data during the past few years are now pointing to the "wait and see" approach as a reasonable initial strategy because many patients can live a long life with the disease without having symptoms. When symptoms appear or there is a risk of functional impairment, a wide spectrum of therapies (local and systemic) can be useful in improving symptoms and controlling the disease. Because of the low incidence of desmoid-type fibromatosis, there is scarce scientific evidence supporting any specific treatment. Nonetheless, if volumetric responses are needed, chemotherapy may be a reasonable early option. However, if long-term control of disease is desirable, hormonal therapy, NSAIDs, and TKIs are the likely treatments of choice. Recent new findings in the biologic development of these tumors, such as the role of Wnt/β-catenin dependent pathway, have shown that the prognostic information provided by specific CTNNB1 gene mutations and other genetic profiles can lead to better methods of selecting patients as candidates for other approaches. Based on recent research, the Notch pathway inhibition in DF is one of the most promising potential targets to explore. As an orphan disease, it is mandatory that as many patients as possible be included in clinical trials.

Biology and Treatment of Aggressive Fibromatosis or Desmoid Tumor

Aggressive fibromatosis, also known as desmoid-type fibromatosis (DTF) or desmoid tumor, is an uncommon locally invasive tumor. Because of its low incidence and variable behavior, DTF is often first seen by physicians who are not familiar with it, and recent advances in understanding this disease have led to changes in treatment approaches. The Wnt (β-catenin) pathway appears to play a key role in DTF pathogenesis, and recent studies of DTF biology suggest a possible model of DTF pathogenesis. Histologically, DTF shows a poorly circumscribed proliferation of myofibroblast-like cells with variable collagen deposition, similar to the proliferative phase of wound healing, and DTF has been associated with trauma and pregnancy. Desmoid-type fibromatosis may be a useful model of the tumor stroma in carcinomas as well as other fibrosing diseases such as progressive pulmonary fibrosis. The clinical course of DTF can vary greatly among patients, complicating the determination of the optimal treatment approach. Treatment options include surgery, nonsteroidal anti-inflammatory drugs with or without hormonal manipulation, chemotherapy, radiation therapy, and other forms of local therapy. Many treatments have been used, but these are not without toxicities. Because of the variable nature of the disease and the potential morbidity of treatment, some cases of DTF may do better without treatment; simple observation is often the best initial treatment. This review used a PubMed search from January 1, 1980, through October 31, 2016, using the terms fibromatosis and desmoid and discusses DTF disease characteristics, pathophysiology, and treatment options as well as examines several cases illustrating key points in the biology and treatment of this heterogeneous disease.

Clinical Activity of the γ-Secretase Inhibitor PF-03084014 in Adults With Desmoid Tumors (Aggressive Fibromatosis)

Purpose Desmoid tumors (aggressive fibromatosis) arise from connective tissue cells or fibroblasts. In general, they are slow growing and do not metastasize; however, locally aggressive desmoid tumors can cause severe morbidity and loss of function. Disease recurrence after surgery and/or radiation and diagnosis of multifocal desmoid tumors highlight the need to develop effective systemic treatments for this disease. In this study, we evaluate objective response rate after therapy with the γ-secretase inhibitor PF-03084014 in patients with recurrent, refractory, progressive desmoid tumors. Patients and Methods Seventeen patients with desmoid tumors received PF-03084014 150 mg orally twice a day in 3-week cycles. Response to treatment was evaluated at cycle 1 and every six cycles, that is, 18 weeks, by RECIST (Response Evaluation Criteria in Solid Tumors) version 1.1. Patient-reported outcomes were measured at baseline and at every restaging visit by using the MD Anderson Symptoms Inventory. Archival tumor and blood samples were genotyped for somatic and germline mutations in APC and CTNNB1. Results Of 17 patients accrued to the study, 15 had mutations in APC or CTNNB1 genes. Sixteen patients (94%) were evaluable for response; five (29%) experienced a confirmed partial response and have been on study for more than 2 years. Another five patients with prolonged stable disease as their best response remain on study. Patient-reported outcomes confirmed clinician reporting that the investigational agent was well tolerated and, in subgroup analyses, participants who demonstrated partial response also experienced clinically meaningful and statistically significant improvements in symptom burden. Conclusion PF-03084014 was well tolerated and demonstrated promising clinical benefit in patients with refractory, progressive desmoid tumors who receive long-term treatment.

[Uncommon mammary-type myofibroblastoma unlike any other: about a case]

Mammary-type myofibroblastoma (MTMF) is a rare benign mesenchymal tumor, initially detected in the breast. Its diagnosis is based on a spectrum of clinical, radiological and possibly histological parameters. We here report the rare case of a 50 year old male patient with mammary-type myofibroblastoma located in the axillary region. The peculiarity of our case lies in the presence of numerous mitoses and this was rarely described in the literature. The aim of our case study was to raise the problem of differential diagnosis of this rare tumor.

Nuclear expression and/or reduced membranous expression of β-catenin correlate with poor prognosis in colorectal carcinoma: A meta-analysis

BACKGROUND

The differential subcellular localizations of β-catenin (including membrane, cytoplasm, and nucleus) play different roles in the progression of colorectal cancer (CRC). However, the correlation between each subcellular localization of β-catenin and the prognosis of CRC patients remains undetermined.

METHODS

Systematic strategies were applied to search for eligible published studies in the PubMed, Embase, and Web of Science databases. The correlation between each subcellular localizations of β-catenin expression and patients' clinicopathological features or prognosis was analyzed.

RESULTS

Finally, this meta-analysis, including 6238 cases from 34 studies, revealed that β-catenin overexpression in the nucleus (HR: 1.50[95% CI: 1.08-2.10]) or reduced expression of β-catenin in the membrane (HR: 1.33[95% CI: 1.15-1.54]) significantly correlated with lower 5-year overall survival (OS). Conversely, overexpression of β-catenin in the cytoplasm (HR: 1.00[95% CI: 0.85-1.18]) did not show significant association with 5-year OS.

CONCLUSION

This study suggested that β-catenin overexpression in the nucleus or reduced expression in the membrane, but not its overexpression in cytoplasm, could serve as a valuable prognostic predictor for CRC. However, additional large and well-designed prospective studies are required to verify our results.

Tailored Beta-catenin mutational approach in extra-abdominal sporadic desmoid tumor patients without therapeutic intervention

Background

The efficacy of the classical treatment modalities surgery and radiotherapy in the treatment of aggressive fibromatosis is presently disputed and there is a shift towards a more conservative approach. The aim of the present study is to objectify tumor growth in patients with extra-abdominal or abdominal wall aggressive fibromatosis, while adhering to a “watchful waiting” policy. Other objectives are to investigate quality of life and to identify factors associated with tumor growth, in particular the relation with the presence of a CTNNB1-gene mutation in the tumor.

Design and methods

GRAFITI is a nationwide, multicenter, prospective registration trial. All patients with extra-abdominal or abdominal wall aggressive fibromatosis are eligible for inclusion in the study. Main exclusion criteria are: history of familiar adenomatous polyposis, severe pain, functional impairment, life/limb threating situations in case of progressive disease. Patients included in the study will be treated with a watchful waiting policy during a period of 5 years. Imaging studies with ultrasound and magnetic resonance imaging scan will be performed during follow-up to monitor possible growth: the first years every 3 months, the second year twice and the yearly. In addition patients will be asked to complete a quality of life questionnaire on specific follow-up moments. The primary endpoint is the rate of progression per year, defined by the Response Evaluation Criteria In Solid Tumors (RECIST). Secondary endpoints are quality of life and the rate of influence on tumor progression for several factors, such as CTNNB1-mutations, age and localization.

Discussion

This study will provide insight in tumor behavior, the effect on quality of life and clinicopathological factors predictive of tumor progression.

Trial registration

The GRAFITI trial is registered in the Netherlands National Trial Register (NTR), number 4714.

Integrating Molecular Testing in the Diagnosis and Management of Children with Thyroid Lesions

Thyroid nodules occur in 1-2% of children, and identifying which nodules are malignant is often challenging. Cytologic evaluation facilitates the diagnosis of thyroid lesions (TLs), but in 10-40% of cases the interpretation is indeterminate. Patients with indeterminate diagnoses are often treated with hemithyroidectomy followed by completion thyroidectomy, if cancer is found in the initial specimen. Exposing patients to multiple surgeries increases costs and morbidity. The American Thyroid Association states that a combination of molecular markers is likely to optimize the management of patients with indeterminate cytology. However, few studies have addressed the molecular alterations present in pediatric TL. Twenty-seven thyroid carcinomas from patients 10 to 19 years of age were tested for alterations common in adult TL, including BRAF V600E mutation, RET fusions, and TERT promoter mutations. Mutation-negative cases were subsequently analyzed with a next-generation sequencing (NGS) mutation panel to search for additional targets. Histologic diagnoses included 12 classic papillary thyroid carcinomas (PTCs), 13 follicular variant PTCs, 1 medullary thyroid carcinoma, and 1 follicular carcinoma. Fourteen cases showed lymph node involvement, and 13 cases demonstrated lymphovascular invasion. The BRAF V600E mutation was detected in 10/27 cases, and RET fusions were detected in 6/27 cases. No TERT promoter mutations were identified in any of the cases. The NGS panel revealed additional RET and CTNNB1 pathogenic missense mutations. Our results demonstrate that molecular abnormalities are common in pediatric TLs and suggest that incorporation of molecular testing will be helpful in optimizing patient management.

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.

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.

Expression and mutation pattern of β-catenin and adenomatous polyposis coli in colorectal cancer patients

BACKGROUND AND AIMS

β-Catenin and adenomatous polyposis coli (APC) are major components of the Wnt pathway. This study aimed to investigate the expression of β-catenin and APC in tumors and lymph nodes in colorectal cancer (CRC) patients and the mutational spectrum of the genes coding these proteins.

METHODS

Expression of APC and β-catenin was examined in 124 tumors and 41 lymph nodes. Exon 3 of CTNNB1 and the mutation cluster region (MCR) in exon 15 of the APC gene were screened for mutation by PCR-sequencing.

RESULTS

Nuclear/cytoplasmic immunostaining of β-catenin was detected in 58.1 and 48.8% in tumors and lymph nodes, respectively. In tumors, abnormal expression of β-catenin correlated with tumor size and with those in lymph nodes. Membranous β-catenin expression occurred in 41.9 and 14.6% of tumors and lymph nodes, respectively. In tumors, lack of membranous β-catenin correlated with high invasiveness and metastatic potential. Positive immunostaining for APC was observed in 2 and 14% of tumors and lymph nodes, respectively. Overexpression in nucleus/cytoplasm and lack of membranous β-catenin significantly correlated with a reduced overall survival. Among 25 tumors, four harbour mutation in Ser33 and Ser47 and overexpress the β-catenin in the nucleus/cytoplasm. Mutations were identified in the APC gene in 13 tumors and six mutations were novel.

CONCLUSIONS

Positive association between aberrant expression of β-catenin in the nucleus/cytoplasm of tumors and lymph nodes was observed. Nucleus/cytoplasmic accumulation of β-catenin and loss of membranous expression are related to reduced survival and could serve as a candidate prognostic predictor.

Activating FGFR2-RAS-BRAF mutations in ameloblastoma

PURPOSE

Ameloblastoma is an odontogenic neoplasm whose overall mutational landscape has not been well characterized. We sought to characterize pathogenic mutations in ameloblastoma and their clinical and functional significance with an emphasis on the mitogen-activated protein kinase (MAPK) pathway.

EXPERIMENTAL DESIGN

A total of 84 ameloblastomas and 40 non-ameloblastoma odontogenic tumors were evaluated with a combination of BRAF V600E allele-specific PCR, VE1 immunohistochemistry, the Ion AmpliSeq Cancer Hotspot Panel, and Sanger sequencing. Efficacy of a BRAF inhibitor was evaluated in an ameloblastoma-derived cell line.

RESULTS

Somatic, activating, and mutually exclusive RAS-BRAF and FGFR2 mutations were identified in 88% of cases. Somatic mutations in SMO, CTNNB1, PIK3CA, and SMARCB1 were also identified. BRAF V600E was the most common mutation, found in 62% of ameloblastomas and in ameloblastic fibromas/fibrodentinomas but not in other odontogenic tumors. This mutation was associated with a younger age of onset, whereas BRAF wild-type cases arose more frequently in the maxilla and showed earlier recurrences. One hundred percent concordance was observed between VE1 immunohistochemistry and molecular detection of BRAF V600E mutations. Ameloblastoma cells demonstrated constitutive MAPK pathway activation in vitro. Proliferation and MAPK activation were potently inhibited by the BRAF inhibitor vemurafenib.

CONCLUSIONS

Our findings suggest that activating FGFR2-RAS-BRAF mutations play a critical role in the pathogenesis of most cases of ameloblastoma. Somatic mutations in SMO, CTNNB1, PIK3CA, and SMARCB1 may function as secondary mutations. BRAF V600E mutations have both diagnostic and prognostic implications. In vitro response of ameloblastoma to a BRAF inhibitor suggests a potential role for targeted therapy.

CTNNB1 S45F mutation predicts poor efficacy of meloxicam treatment for desmoid tumors: a pilot study

We hypothesized that patterns of CTNNB1 (β-catenin) mutations would affect the outcome of conservative therapy in patients with desmoid tumors. This study aimed to determine the significance of CTNNB1 (β-catenin) mutations in predicting the treatment outcome in patients with desmoid tumors treated with meloxicam, a cyclooxygenase-2 (COX-2) selective inhibitor. Between 2003 and 2012, consecutive thirty-three patients with extra-peritoneal sporadic desmoid tumors were prospectively treated with meloxicam as the initial systemic medical therapy. The efficacy of meloxicam was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST). DNA was isolated from frozen tissue or formalin-fixed materials. CTNNB1 mutation analysis was performed by direct sequencing. Positivity of nuclear β-catenin staining by immunohistochemistry was compared with the status of CTNNB1 mutations. The correlation between the efficacy of meloxicam treatment and status of CTNNB1 mutations was analyzed. Of the 33 patients with meloxicam treatment, one showed complete remission (CR), 7 partial remission (PR), 12 stable disease (SD), and 13 progressive disease (PD). The following 3 point mutations were identified in 21 of the 33 cases (64%): T41A (16 cases), S45F (4 cases) and S45P (one case). The nuclear expression of β-catenin correlated significantly with CTNNB1 mutation status (p = 0.035); all four cases with S45F mutation exhibited strong nuclear expression of β-catenin. S45F mutation was significantly associated with a poor response (all cases; PD) (p = 0.017), whereas the other mutations had no impact on efficacy. The CTNNB1 mutation status was of significant prognostic value for meloxicam treatment in patients with sporadic desmoid tumors.

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.

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.

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.

CTNNB1 genotyping and APC screening in pediatric desmoid tumors: a proposed algorithm

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.

Extra-abdominal desmoid tumours: a review of the literature

Extra-abdominal desmoid lesions, otherwise known as aggressive fibromatosis, are slow-growing benign lesions which may be encountered in clinical practice. Recent controversies exist regarding their optimal treatment. Given their benign nature, is major debulking surgery justified, or is it worth administering chemotherapy for a disease process which unusually defies common teaching and responds to such medications? We present a literature review of this particular pathology discussing the aetiology, clinical presentation, and various current controversies in the treatment options.

Pathology of gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is a well recognized and relatively well understood soft tissue tumor. Early events in GIST development are activating mutations in KIT or PDGFRA, which occur in most GISTs and encode for mutated tyrosine receptor kinases that are therapeutic targets for tyrosine kinase inhibitors, including imatinib and sunitinib. A small minority of GISTs possessing neither KIT nor PDGFRA mutations may have germline mutations in SDH, suggesting a potential role of SDH in the pathogenesis. Immunohistochemical detection of KIT, and more recently DOG1, has proven to be reliable and useful in the diagnosis of GISTs. Because current and future therapies depend on pathologists, it is important that they recognize KIT-negative GISTs, GISTs in specific clinical contexts, GISTs with unusual morphology, and GISTs after treatment. This review focuses on recent developments in the understanding of the biology, immunohistochemical diagnosis, the role of molecular analysis, and risk assessment of GISTs.

Fibroblastic and myofibroblastic tumors in children and adolescents

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.