Intracranial chondromas: A histopathologic and molecular study of three cases.

AIMS: Meningeal chondromas constitute a small fraction of central nervous system tumors, with only 61 cases reported in the literature. Somatic mutations of IDH1/2 genes have been described in enchondromas, and, in soft-tissue chondromas, rearrangements of the HMGA2 gene have been reported. The aim of our study was to perform molecular analyses of 3 additional cases and to do a complete review of the literature to better characterize this rare entity. MATERIALS AND METHODS: Here, we report 3 cases of primitive meningeal chondromas in children and young adults. Immunohistochemical analyses for HMGA2 and IDH1R132H, molecular analyses of IDH1/2 mutations, and FISH analysis of the HMGA2 locus were performed. RESULTS: Immunohistochemical analyses of all cases were negative for IDH1R132H and HMGA2 proteins. Molecular analyses failed to reveal IDH1/2 mutations, and FISH analyses did not evidence any HMGA2 rearrangements. Similarly to what is reported in the literature, the 3 meningeal chondromas in this study were benign tumors with no recurrence after complete resection with a follow-up of 85, 46, and 89 months. CONCLUSION: Meningeal chondroma is rare. It affects predominantly young adults and has a good outcome. No molecular alterations have currently been described in this entity.

Synovial chondromatosis and soft tissue chondroma: extraosseous cartilaginous tumor defined by FN1 gene rearrangement.

A fusion between fibronectin 1 (FN1) and activin receptor 2A (ACVR2A) has been reported previously in isolated cases of the synovial chondromatosis. To analyze further and validate the findings, we performed FISH and demonstrated recurrent FN1-ACVR2A rearrangements in synovial chondromatosis (57%), and chondrosarcoma secondary to synovial chondromatosis (75%), showing that FN1 and/or AVCR2A gene rearrangements do not distinguish between benign and malignant synovial chondromatosis. RNA sequencing revealed the presence of the FN1-ACVR2A fusion in several cases that were negative by FISH suggesting that the true prevalence of this fusion is potentially higher than 57%. In soft tissue chondromas, FN1 alterations were detected by FISH in 50% of cases but no ACVR2A alterations were identified. RNA sequencing identified a fusion involving FN1 and fibroblast growth factor receptor 2 (FGFR2) in the case of soft tissue chondroma and FISH confirmed recurrent involvement of both FGFR1 and FGFR2. These fusions were present in a subset of soft tissue chondromas characterized by grungy calcification, a feature reminiscent of phosphaturic mesenchymal tumor. However, unlike the latter, fibroblast growth factor 23 (FGF23) mRNA expression was not elevated in soft tissue chondromas harboring the FN1-FGFR1 fusion. The mutual exclusivity of ACVR2A rearrangements observed in synovial chondromatosis and FGFR1/2 in soft tissue chondromas suggests these represent separate entities. There have been no reports of malignant soft tissue chondromas, therefore differentiating these lesions will potentially alter clinical management by allowing soft tissue chondromas to be managed more conservatively.

Paragangliomas in Carney-Stratakis Syndrome.

Carney-Stratakis Syndrome (CSS) comprises of paragangliomas (PGLs) and gastrointestinal stromal tumors (GISTs). Several of its features overlap with Carney Triad (CT) - PGLs, GISTs, and pulmonary chondromas. CSS has autosomal dominant inheritance, incomplete penetrance, and greater relative frequency of PGL over GISTs. The PGLs in CSS are multicentric and GISTs are multifocal in all the patients, suggesting an inherited susceptibility and associating the two manifestations. In this review, we highlight the clinical, pathological, and molecular characteristics of CSS, along with its diagnostic and therapeutic implications.

MTNR1B loss promotes chordoma recurrence by abrogating melatonin-mediated ß-catenin signaling repression.

Chordoma is an extremely rare malignant bone tumor with a high rate of relapse. While cancer stem cells (CSCs) are closely associated with tumor recurrence, which depend on its capacity to self-renew and induce chemo-/radioresistance, whether and how CSCs participate in chordoma recurrence remains unclear. The current study found that tumor cells in recurrent chordoma displayed more dedifferentiated CSC-like properties than those in corresponding primary tumor tissues. Meanwhile, MTNR1B deletion along with melatonin receptor 1B (MTNR1B) down-regulation was observed in recurrent chordoma. Further investigation revealed that activation of Gαi2 by MTNR1B upon melatonin stimulation could inhibit SRC kinase activity via recruiting CSK and SRC, increasing SRC Y530 phosphorylation, and decreasing SRC Y419 phosphorylation. This subsequently suppressed ß-catenin signaling and stemness via decreasing ß-catenin p-Y86/Y333/Y654. However, MTNR1B loss in chordoma mediated increased CSC properties, chemoresistance, and tumor progression by releasing melatonin's repression of ß-catenin signaling. Clinically, MTNR1B deletion was found to correlate with patients' survival. Together, our study establishes a novel convergence between melatonin and ß-catenin signaling pathways and reveals the significance of this cross talk in chordoma recurrence. Besides, we propose that MTNR1B is a potential biomarker for prediction of chordoma prognosis and selection of treatment options, and chordoma patients might benefit from targeting MTNR1B/Gαi2/SRC/ß-catenin axis.

FGFR3 Deficiency Causes Multiple Chondroma-like Lesions by Upregulating Hedgehog Signaling.

Most cartilaginous tumors are formed during skeletal development in locations adjacent to growth plates, suggesting that they arise from disordered endochondral bone growth. Fibroblast growth factor receptor (FGFR)3 signaling plays essential roles in this process; however, the role of FGFR3 in cartilaginous tumorigenesis is not known. In this study, we found that postnatal chondrocyte-specific Fgfr3 deletion induced multiple chondroma-like lesions, including enchondromas and osteochondromas, adjacent to disordered growth plates. The lesions showed decreased extracellular signal-regulated kinase (ERK) activity and increased Indian hedgehog (IHH) expression. The same was observed in Fgfr3-deficient primary chondrocytes, in which treatment with a mitogen-activated protein kinase (MEK) inhibitor increased Ihh expression. Importantly, treatment with an inhibitor of IHH signaling reduced the occurrence of chondroma-like lesions in Fgfr3-deficient mice. This is the first study reporting that the loss of Fgfr3 function leads to the formation of chondroma-like lesions via downregulation of MEK/ERK signaling and upregulation of IHH, suggesting that FGFR3 has a tumor suppressor-like function in chondrogenesis.

Use of MicroRNA biomarkers to distinguish enchondroma from low-grade chondrosarcoma.

Establishing a definitive diagnosis between benign enchondroma versus low-grade chondrosarcoma presents a potential challenge to both clinicians and pathologists. microRNAs (small non-coding RNAs) have proven to be effective biomarkers for the identification of tumors and tumor progression. We present analysis, both array and quantitative PCR, that shows consistently and substantially increased expression of two microRNAs, miRs-181a and -138, in low-grade chondrosarcomas compared with enchondromas. The data suggest these microRNAs would provide an analytical distinction between the chondrosarcoma and benign neoplasms that can be performed in formalin-fixed paraffin-embedded specimens. Together with recent publications, these data indicate that miRs-181a and -138 also play a role in tumor development and homeostasis and may provide new targets for the development of much needed therapeutic intervention.

SHP2 regulates chondrocyte terminal differentiation, growth plate architecture and skeletal cell fates.

Loss of PTPN11/SHP2 in mice or in human metachondromatosis (MC) patients causes benign cartilage tumors on the bone surface (exostoses) and within bones (enchondromas). To elucidate the mechanisms underlying cartilage tumor formation, we investigated the role of SHP2 in the specification, maturation and organization of chondrocytes. Firstly, we studied chondrocyte maturation by performing RNA-seq on primary chondrocyte pellet cultures. We found that SHP2 depletion, or inhibition of the ERK1/2 pathway, delays the terminal differentiation of chondrocytes from the early-hypertrophic to the late-hypertrophic stage. Secondly, we studied chondrocyte maturation and organization in mice with a mosaic postnatal inactivation of Ptpn11 in chondrocytes. We found that the vertebral growth plates of these mice have expanded domains of early-hypertrophic chondrocytes that have not yet terminally differentiated, and their enchondroma-like lesions arise from chondrocytes displaced from the growth plate due to a disruption in the organization of maturation and ossification zones. Furthermore, we observed that lesions from human MC patients also display disorganized chondrocyte maturation zones. Next, we found that inactivation of Ptpn11 in Fsp1-Cre-expressing fibroblasts induces exostosis-like outgrowths, suggesting that loss of SHP2 in cells on the bone surface and at bone-ligament attachment sites induces ectopic chondrogenesis. Finally, we performed lineage tracing to show that exostoses and enchondromas in mice likely contain mixtures of wild-type and SHP2-deficient chondrocytes. Together, these data indicate that in patients with MC, who are heterozygous for inherited PTPN11 loss-of-function mutations, second-hit mutations in PTPN11 can induce enchondromas by disrupting the organization and delaying the terminal differentiation of growth plate chondrocytes, and can induce exostoses by causing ectopic chondrogenesis of cells on the bone surface. Furthermore, the data are consistent with paracrine signaling from SHP2-deficient cells causing SHP2-sufficient cells to be incorporated into the lesions.

Convexity dural chondroma: a case report with pathological and molecular analysis.

Chondromas are rare benign tumors that commonly originate from the base of the skull, while those arising from the dura mater are less common. Although the molecular mechanism underlying its pathogenesis remains largely unknown, 12q13-15 rearrangements followed by the activation of HMGA2, which is associated with cell proliferation, have been reported in soft tissue chondromas. A recent comprehensive analysis of mesenchymal tumors identified an IDH1/2 mutation in cartilaginous tumors. However, these alterations have not yet been examined in dural chondromas. We here described clinical and pathological features in a new case of convexity dural chondroma with the wildtype IDH1/2 and expression of HMGA2 and reviewed the relevant literature.

Gastrointestinal stromal tumour.

Gastrointestinal stromal tumours (GISTs) are mesenchymal neoplasms that arise in the gastrointestinal tract, usually in the stomach or the small intestine and rarely elsewhere in the abdomen. They can occur at any age, the median age being 60-65 years, and typically cause bleeding, anaemia, and pain. GISTs have variable malignant potential, ranging from small lesions with a benign behaviour to fatal sarcomas. Most tumours stain positively for the mast/stem cell growth factor receptor KIT and anoctamin 1 and harbour a kinase-activating mutation in either KIT or PDGFRA. Tumours without such mutations could have alterations in genes of the succinate dehydrogenase complex or in BRAF, or rarely RAS family genes. About 60% of patients are cured by surgery. Adjuvant treatment with imatinib is recommended for patients with a substantial risk of recurrence, if the tumour has an imatinib-sensitive mutation. Tyrosine kinase inhibitors substantially improve survival in advanced disease, but secondary drug resistance is common.

[Gastrointestinal stromal tumor (GIST): advances in 2013]. / Gastrointestinální stromální tumor (GIST): pokroky do roku 2013.

Gastrointestinal stromal tumors (GIST) are currently regarded as a heterogenous group of tumors sharing common histological appearance, KIT immunopositivity and supposed origin from tissue progenitor cells capable of differentiation into the phenotype of Cajal interstitial cells. GISTs can be divided according to immunoexpression of the beta subunit of mitochondrial enzyme succinate dehydrogenase (SDHB) to SDHB-positive (encompassing KIT, PDGFRA and NF1 mutated GISTs), and SDHB-deficient GISTs (including Carney-Stratakis syndrome, Carney triad, sporadic pediatric GISTs, and a small subset of sporadic adult GISTs). The individual molecular subtypes differ in biological behavior and in their response to systemic targeted therapy, which is indicated in metastatic GISTs or in tumors with high risk of recurrence. Although several risk-stratification classifications have been developed, strictly defined criteria to identify patients at risk are still lacking. Pharmacogenomics have been successful in designing drugs to overcome not only the primary resistance of GISTs to the action of imatinib (e.g. GISTs with a substitution of Asp842Val in exon 18 PDGFRA or SDHB-deficient GISTs), but also the secondary resistance caused by secondary mutation of a gene encoding either the receptor tyrosine kinase or other molecules involved in the respective signalling cascade. Future directions concentrate on rational molecular targeting for systemic therapy based on complex genetic investigation of the tumor. Peripheral blood is planned to be used as a source of information for genetic events responsible for the secondary resistance of metastatic tumors.

Extraskeletal chondroma of the toe in a child with DICER1 tumor predisposition syndrome: support for a dominant negative mechanism.

DICER1 tumor predisposition syndrome is a pleiotropic disorder that gives rise to various mainly pediatric-onset lesions. We report an extraskeletal chondroma (EC) of the great toe occurring in a child who, unusually, carries a germline "hotspot" missense DICER1 variant rather than the more usual loss-of-function (LOF) variant. No heterozygous LOF allele was identified in the EC. We demonstrate this variant impairs 5p cleavage of precursor-miRNA (pre-miRNA) and competes with wild-type (WT) DICER1 protein for pre-miRNA processing. These results suggest a mechanism through which a germline RNase IIIb variant could impair pre-miRNA processing without complete LOF of the WT DICER1 allele.

IDH1 and IDH2 mutations are frequent events in central chondrosarcoma and central and periosteal chondromas but not in other mesenchymal tumours.

Somatic mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 occur in gliomas and acute myeloid leukaemia (AML). Since patients with multiple enchondromas have occasionally been reported to have these conditions, we hypothesized that the same mutations would occur in cartilaginous neoplasms. Approximately 1200 mesenchymal tumours, including 220 cartilaginous tumours, 222 osteosarcomas and another ∼750 bone and soft tissue tumours, were screened for IDH1 R132 mutations, using Sequenom(®) mass spectrometry. Cartilaginous tumours and chondroblastic osteosarcomas, wild-type for IDH1 R132, were analysed for IDH2 (R172, R140) mutations. Validation was performed by capillary sequencing and restriction enzyme digestion. Heterozygous somatic IDH1/IDH2 mutations, which result in the production of a potential oncometabolite, 2-hydroxyglutarate, were only detected in central and periosteal cartilaginous tumours, and were found in at least 56% of these, ∼40% of which were represented by R132C. IDH1 R132H mutations were confirmed by immunoreactivity for this mutant allele. The ratio of IDH1:IDH2 mutation was 10.6 : 1. No IDH2 R140 mutations were detected. Mutations were detected in enchondromas through to conventional central and dedifferentiated chondrosarcomas, in patients with both solitary and multiple neoplasms. No germline mutations were detected. No mutations were detected in peripheral chondrosarcomas and osteochondromas. In conclusion, IDH1 and IDH2 mutations represent the first common genetic abnormalities to be identified in conventional central and periosteal cartilaginous tumours. As in gliomas and AML, the mutations appear to occur early in tumourigenesis. We speculate that a mosaic pattern of IDH-mutation-bearing cells explains the reports of diverse tumours (gliomas, AML, multiple cartilaginous neoplasms, haemangiomas) occurring in the same patient.

Thorahcic SMARCA4-deficient undifferentiated tumors with ganglioneuroma and enchondroma: implications for SLC7A11 and ARID1A expression: a case report.

BACKGROUND: SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4-deficient thoracic sarcoma (SMARCA4-DTS) is a rare disease that has recently been described as an entity. It is characterized by an aggressive clinical course and specific genetic alterations. As an immunohistological feature, the tumors are deficient in SMARCA4 and SMARCA2 and express sex-determining region Y (SRY)-box 2 (SOX2). Occasionally, there are cases that are less frequent and difficult to distinguish from SMARCA4-deficient non-small cell lung carcinoma (SMARCA4-dNSCLC). Therefore, the 5th edition of the World Health Organization (WHO) classification describes thoracic SMARCA 4-deficient undifferentiated tumors (SMARCA4-UT). In contrast, Carney's triad is a syndrome that combines three rare soft tissue tumors: gastric leiomyosarcoma, pulmonary chondroma, and extra-adrenal paraganglioma. Protein kinase cAMP-dependent type I regulatory subunit alpha (PRKAR1A) has been proposed as the causative gene. Both diseases are valuable cases; moreover, there have been no previous reports of their coexistence. CASE PRESENTATION: A 43-year-old man visited our hospital because of respiratory distress. Computed tomography revealed a large mass measuring 55 mm in the upper lobe of the right lung and front mediastinum, with metastases in the surrounding lymph nodes. Needle biopsy was performed for diagnosis, and histological examination of the samples revealed monotonous epithelioid-like cells with loose binding and sheet-form proliferation. The tumor cells had distinct nuclei with some rhabdoid-like cells. Immunohistochemical analysis revealed that the tumor cells were positive for AE1AE3, SOX2, CD34, and p53 and negative for SMARCA4 and SMARCA2. The patient died 6 months after admission, without any treatment. Autopsy revealed ganglioneuroma and enchondroma suggestive of an incomplete Carney complex. CONCLUSION: SMARCA4-UT is a rare and recently established disease. While it is difficult to diagnose, it is necessary to distinguish undifferentiated carcinoma, large cell carcinoma, Ewing sarcoma, and epithelioid sarcoma when diagnosing tumors involving the mediastinum. Moreover, cases of SMARCA4-UT with ganglioneuroma and enchondroma are very rare. We discuss and report a case of SMARCA4-UT in which we also examined ARID1A and SLC7A11expression.

Distinct Roles of Glutamine Metabolism in Benign and Malignant Cartilage Tumors With IDH Mutations.

Enchondromas and chondrosarcomas are common cartilage neoplasms that are either benign or malignant, respectively. The majority of these tumors harbor mutations in either IDH1 or IDH2. Glutamine metabolism has been implicated as a critical regulator of tumors with IDH mutations. Using genetic and pharmacological approaches, we demonstrated that glutaminase-mediated glutamine metabolism played distinct roles in enchondromas and chondrosarcomas with IDH1 or IDH2 mutations. Glutamine affected cell differentiation and viability in these tumors differently through different downstream metabolites. During murine enchondroma-like lesion development, glutamine-derived α-ketoglutarate promoted hypertrophic chondrocyte differentiation and regulated chondrocyte proliferation. Deletion of glutaminase in chondrocytes with Idh1 mutation increased the number and size of enchondroma-like lesions. In contrast, pharmacological inhibition of glutaminase in chondrosarcoma xenografts reduced overall tumor burden partially because glutamine-derived non-essential amino acids played an important role in preventing cell apoptosis. This study demonstrates that glutamine metabolism plays different roles in tumor initiation and cancer maintenance. Supplementation of α-ketoglutarate and inhibiting GLS may provide a therapeutic approach to suppress enchondroma and chondrosarcoma tumor growth, respectively. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Benign bone tumors--recent developments.

Benign bone tumors frequently pose a diagnostic challenge for general surgical pathologists. Accurate pathologic diagnosis requires careful clinical and radiological correlation. The most significant recent advances in some benign bone tumors have occurred at the molecular and cytogenetic level. The detection of clonal chromosomal aberrations, various specific molecular genetic events, and the description of the bone cell signaling pathways in the field of osteoimmunology have provided a better understanding of the pathophysiology of certain tumors and an important aid in the diagnostic workup and differential diagnosis of some bone lesions demonstrating overlapping clinical and pathologic features. Future directions include prognostic and therapeutic applications of these findings. Newer less invasive therapeutic techniques and medical management have been developed for the treatment of certain benign bone tumors.

Benign Cartilage-forming Tumors.

Although uncommon in many pathology practices, cartilage-forming tumors represent some of the most frequent primary bone tumors. Diagnosis can be challenging given their variable histologic spectrum and the presence of overlapping morphologic, immunohistochemical, and genetic features between benign and malignant entities, particularly low-grade malignancies. Correlation with clinical findings and radiographic features is crucial for achieving an accurate diagnosis and appropriate clinical management, ranging from observation to excision. Tumors can be characterized broadly by their location in relation to the bone (surface or intramedullary). In specific instances, ancillary testing may help.

Carney Triad, Carney-Stratakis Syndrome, 3PAS and Other Tumors Due to SDH Deficiency.

Succinate dehydrogenase (SDH) is a key respiratory enzyme that links Krebs cycle and electron transport chain and is comprised of four subunits SDHA, SDHB, SDHC and SDHD. All SDH-deficient tumors are caused by or secondary to loss of SDH activity. As many as half of the familial cases of paragangliomas (PGLs) and pheochromocytomas (PHEOs) are due to mutations of the SDHx subunits. Gastrointestinal stromal tumors (GISTs) associated with SDH deficiency are negative for KIT/PDGFRA mutations and present with distinctive clinical features such as early onset (usually childhood or adolescence) and almost exclusively gastric location. SDH-deficient GISTs may be part of distinct clinical syndromes, Carney-Stratakis syndrome (CSS) or dyad and Carney triad (CT). CSS is also known as the dyad of GIST and PGL; it affects both genders equally and is inherited in an autosomal dominant manner with incomplete penetrance. CT is a very rare disease; PGL, GIST and pulmonary chondromas constitute CT which shows female predilection and may be a mosaic disorder. Even though there is some overlap between CT and CSS, as both are due to SDH deficiency, CSS is caused by inactivating germline mutations in genes encoding for the SDH subunits, while CT is mostly caused by a specific pattern of methylation of the SDHC gene and may be due to germline mosaicism of the responsible genetic defect.

Genomic Profiling of Low-grade Intramedullary Cartilage Tumors Can Distinguish Enchondroma From Chondrosarcoma.

Low-grade intramedullary cartilage tumors include enchondroma and grade 1 chondrosarcoma. Classification based on radiopathologic correlation guides treatment, typically observation for asymptomatic enchondroma and surgery for chondrosarcoma. However, some tumors elude classification because radiographic and morphologic findings are equivocal. To date, no ancillary tests are available to aid the diagnosis of such indeterminate or suspicious tumors. We investigated the genomic landscape of low-grade cartilage tumors to determine the profile. We studied 10 each enchondroma, grade 1 chondrosarcoma, and suspicious cartilage neoplasms, respectively, by capture-based next-generation sequencing targeting 479 cancer genes and copy number. In enchondroma, IDH1 or IDH2 hotspot activating mutations and/or COL2A1 alterations were identified in 70% and 60% of cases, respectively; copy number changes were rare (20%). Suspicious cartilage neoplasms had frequent hotspot mutations in IDH1 or IDH2 and alterations in COL2A1 (90% and 70%, respectively); copy number changes were rare (20%). Overall, 80% of suspicious cartilage neoplasms were genomically indistinguishable from enchondroma. In contrast, 20% of chondrosarcoma had IDH1 or IDH2 alterations, 100% demonstrated alteration of COL2A1, and 70% had genomes with numerous copy number gains and losses. In total, 80% of chondrosarcomas demonstrated additional pathogenic mutations, deep deletions, or focal amplifications in cancer genes, predominantly CDKN2A. These results demonstrate distinct genomic profiles of enchondroma and grade 1 chondrosarcoma. Further, sequencing may aid in the correct classification of diagnostically challenging tumors. Additional pathogenic alterations (such as in CDKN2A) or numerous copy number gains or losses would support a diagnosis of chondrosarcoma although the absence of such findings does not exclude the diagnosis.

circHIPK3 promotes proliferation and migration and invasion via regulation of miR­637/HDAC4 signaling in osteosarcoma cells.

Accumulating evidence has indicated that circular RNAs (circRNAs) serve crucial roles in the progression of a diverse range of different types of cancer, including osteosarcoma (OS). The present study determined the expression pattern and function of circRNA homeodomain interacting protein kinase 3 (circHIPK3), a novel circular RNA, in OS. It was revealed that circHIPK3 expression was upregulated in OS tissue samples and OS cell lines. A localization assay revealed that circHIPK3 was primarily located in the cytoplasm. Using loss­of­function proliferation and Transwell assays, the present study revealed that circHIPK3­knockdown suppressed OS cell proliferation, migration and invasion. Furthermore, the present study screened potential microRNAs that may interact with circHIPK3. It was revealed that microRNA­637 (miR­637) expression was downregulated in OS according to a Gene Expression Omnibus data analysis. In addition, the present study demonstrated that miR­637 expression was downregulated in OS cell lines. A fluorescence in situ hybridization assay revealed that both miR­637 and circHIPK3 were located in the cytoplasm. An in­depth mechanism investigation demonstrated that circHIPK3 expression was inversely correlated with miR­637 expression, and that circHIPK3 was a target of miR­637. In addition, it was revealed that histone deacetylase 4 (HDAC4) was another downstream target gene of miR­637, as demonstrated using a luciferase assay. It was revealed that miR­637 suppressed OS cell proliferation, migration and invasion via targeting of HDAC4. Finally, the present study demonstrated that circHIPK3 sponged miR­637 to promote HDAC4 expression and OS cell proliferation, migration and invasion. In conclusion, the present study uncovered the role of the circHIPK3/miR­637/HDAC4 axis in OS cell proliferation, migration and invasion. It was demonstrated that circHIPK3 promoted OS cell proliferation, migration and invasion by modulating miR­637/HDAC4 signaling.

SDHC Methylation Pattern in Patients With Carney Triad.

Carney triad is a multitumor syndrome affecting almost exclusively young women in a nonfamilial setting, which manifests by multifocal gastric gastrointestinal stromal tumors, paragangliomas, and pulmonary chondroma. The Carney triad-associated tumors are characterized by a deficiency of the mitochondrial succinate dehydrogenase enzymatic complex. Recently, it has been observed that the deficiency results from epigenetic silencing of the SDHC gene by its promoter hypermethylation. To elucidate anatomic distribution of SDHC promoter methylation in Carney triad patients and thus to shed some light on the possible natural development of this epigenetic change, both neoplastic and available non-neoplastic tissues of 3 patients with Carney triad were tested for hypermethylation at the SDHC promoter site. SDHC promoter hypermethylation was proven in all tumors studied. Lack of SDHC epigenetic silencing in the non-neoplastic lymphoid and duodenal tissue (ie, tissues not involved in the development of Carney triad-associated tumors) together with the finding of SDHC promoter hypermethylation in the non-neoplastic gastric wall favors the hypothesis of postzygotic somatic mosaicism as the biological background of Carney triad; it also offers an explanation of the multifocality of gastrointestinal stromal tumors of the stomach occurring in this scenario as well. However, the precise mechanism responsible for the peculiar organ-specific distribution of Carney triad-associated tumors is still unknown.