MyMedR

RANK, RANKL, and OPG in recurrent solid/multicystic ameloblastoma: their distribution patterns and biologic significance

Siar CH, Tsujigiwa H, Ishak I, Hussin NM, Nagatsuka H, Ng KH

Oral Surg Oral Med Oral Pathol Oral Radiol, 2015 Jan;119(1):83-91.

PMID: 25446507 DOI: 10.1016/j.oooo.2014.09.017

To determine the distribution patterns of bone resorption regulators, receptor activator of nuclear factor κ-B (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) in recurrent ameloblastoma (RAs) and to clarify their impact on the biologic behavior of these neoplasms.

Intra-epithelially entrapped blood vessels in ameloblastoma

Siar CH, Ishak I, Ng KH

J Oral Pathol Med, 2015 May;44(5):378-85.

PMID: 25155411 DOI: 10.1111/jop.12247

The ameloblastoma is a benign but locally aggressive odontogenic neoplasm with a high recurrence rate. While significant progress has been made in our understanding regarding the role of tumoral vasculature relative to the diverse behavioral characteristics of this tumor, no attention has been paid to a distinct subset of blood vessels entrapped within its epithelial compartment. As vascular niches are known to influence tumoral growth, clarification of these vessels is important. The objectives of this study were to investigate the morphologic characteristics of intra-epithelially entrapped blood vessels (IEBVs) in ameloblastoma and to speculate on their relevance.

Podoplanin, E-cadherin, β-catenin, and CD44v6 in recurrent ameloblastoma: their distribution patterns and relevance

Siar CH, Ishak I, Ng KH

J Oral Pathol Med, 2015 Jan;44(1):51-8.

PMID: 25059841 DOI: 10.1111/jop.12203

Ameloblastoma is a benign but locally infiltrative odontogenic epithelial neoplasm with a high risk for recurrence. Podoplanin, a lymphatic endothelium marker, putatively promotes collective cell migration and invasiveness in this neoplasm. However, its role in the recurrent ameloblastoma (RA) remains unclear. As morphological, signaling, and genetic differences may exist between primary and recurrent tumors, clarification of their distribution patterns is of relevance.

Identifying factors associated with diagnostic concordance/discordance in oral lichen planus

Siar CH, Lim JS, Tang SP, Chia HS, Loh YM, Ng KH

J Oral Maxillofac Surg, 2013 Oct;71(10):1688-93.

PMID: 23773425 DOI: 10.1016/j.joms.2013.04.026

To identify factors associated with concordance and discordance between clinical and histopathologic diagnoses of oral lichen planus lesions.

Differential expression of transcription factors Snail, Slug, SIP1, and Twist in ameloblastoma

Siar CH, Ng KH

J Oral Pathol Med, 2014 Jan;43(1):45-52.

PMID: 23560539 DOI: 10.1111/jop.12065

Epithelial-to-mesenchymal transition (EMT) via the mechanism of transcription repression is a crucial process for the induction of invasiveness in many human tumors. Ameloblastoma is a benign odontogenic epithelial neoplasm with a locally infiltrative behavior. Twist, an EMT promoter, has been implicated in its invasiveness. The roles of the other transcription factors remain unclarified.

Cementum status in natural teeth opposing implant-borne bridgework in Macaca fascicularis

Siar CH, Pua CK, Toh CG, Romanos G, Ng KH

Oral Surg Oral Med Oral Pathol Oral Radiol, 2012 Nov;114(5 Suppl):S46-53.

PMID: 23083955 DOI: 10.1016/j.tripleo.2011.07.049

The objective of this study was to investigate the cementum status in natural teeth opposing implant-supported bridgework.

Differential expression of canonical and non-canonical Wnt ligands in ameloblastoma

Siar CH, Nagatsuka H, Han PP, Buery RR, Tsujigiwa H, Nakano K, et al.

J Oral Pathol Med, 2012 Apr;41(4):332-9.

PMID: 22077561 DOI: 10.1111/j.1600-0714.2011.01104.x

Canonical and non-canonical Wnt signaling pathways modulate diverse cellular processes during embryogenesis and post-natally. Their deregulations have been implicated in cancer development and progression. Wnt signaling is essential for odontogenesis. The ameloblastoma is an odontogenic epithelial neoplasm of enamel organ origin. Altered expressions of Wnts-1, -2, -5a, and -10a are detected in this tumor. The activity of other Wnt members remains unclarified.

Ameloblastoma of the jaws: a retrospective analysis of 340 cases in a Malaysian population

Siar CH, Lau SH, Ng KH

J Oral Maxillofac Surg, 2012 Mar;70(3):608-15.

PMID: 21723654 DOI: 10.1016/j.joms.2011.02.039

Ameloblastoma of the human jaw is an uncommon but clinically significant odontogenic epithelial neoplasm. The aim was to analyze the clinicopathologic characteristics of ameloblastoma in a Malaysian population.

Subcutaneous reactions and degradation characteristics of collagenous and noncollagenous membranes in a macaque model

Siar CH, Toh CG, Romanos G, Ng KH

Clin Oral Implants Res, 2011 Jan;22(1):113-20.

PMID: 20678135 DOI: 10.1111/j.1600-0501.2010.01970.x

collagenous and noncollagenous membranes have been investigated in many animal systems but their effects in the macaque model are unknown.

Notch4 overexpression in ameloblastoma correlates with the solid/multicystic phenotype

Siar CH, Nagatsuka H, Chuah KS, Rivera RS, Nakano K, Ng KH, et al.

Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2010 Aug;110(2):224-33.

PMID: 20659700 DOI: 10.1016/j.tripleo.2010.03.009

Notch signaling has been implicated in cell fate decisions during odontogenesis and tumorigenesis of some odontogenic neoplasms; however, its role in solid/multicystic (SA), unicystic (UA), and recurrent (RA) ameloblastoma remains unclear. The aim of this study was to determine Notch receptor and ligand expressions in these subtypes and to speculate on their significance.

Differential expression of Notch receptors and their ligands in desmoplastic ameloblastoma

Siar CH, Nakano K, Han PP, Nagatsuka H, Ng KH, Kawakami T

J Oral Pathol Med, 2010 Aug 1;39(7):552-8.

PMID: 20337864 DOI: 10.1111/j.1600-0714.2009.00871.x

In mammals, the Notch gene family encodes four receptors (Notch1-4), and all of them are important for cell fate decisions. Notch signaling pathway plays an essential role in tooth development. The ameloblastoma, a benign odontogenic epithelial neoplasm, histologically recapitulates the enamel organ at bell stage. Notch has been detected in the plexiform and follicular ameloblastoma. Its activity in the desmoplastic ameloblastoma is unknown.

Invadopodia proteins, cortactin, N-WASP and WIP differentially promote local invasiveness in ameloblastoma

Siar CH, Rahman ZA, Tsujigiwa H, Mohamed Om Alblazi K, Nagatsuka H, Ng KH

J Oral Pathol Med, 2016 Sep;45(8):591-8.

PMID: 26752341 DOI: 10.1111/jop.12417

BACKGROUND: Cell migration and invasion through interstitial tissues are dependent upon several specialized characteristics of the migratory cell notably generation of proteolytic membranous protrusions or invadopodia. Ameloblastoma is a benign odontogenic epithelial neoplasm with a locally infiltrative behaviour. Cortactin and MMT1-MMP are two invadopodia proteins implicated in its local invasiveness. Other invadopodia regulators, namely N-WASP, WIP and Src kinase remain unclarified. This study addresses their roles in ameloblastoma.

MATERIALS AND METHOD: Eighty-seven paraffin-embedded ameloblastoma cases (20 unicystic, 47 solid/multicystic, 3 desmoplastic and 17 recurrent) were subjected to immunohistochemistry for expression of cortactin, N-WASP, WIP, Src kinase and F-actin, and findings correlated with clinicopathological parameters.

RESULTS: Invadopodia proteins (except Src kinase) and F-actin were widely detected in ameloblastoma (cortactin: n = 73/87, 83.9%; N-WASP: n = 59/87; 67.8%; WIP: n = 77/87; 88.5%; and F-actin: n = 87/87, 100%). Protein localization was mainly cytoplasmic and/or membranous, and occasionally nuclear for F-actin. Cortactin, which functions as an actin-scaffolding protein, demonstrated significantly higher expression levels within ameloblastoma tumoral epithelium than in stroma (P < 0.05). N-WASP, which coordinates actin polymerization and invadopodia-mediated extracellular matrix degradation, was overexpressed in the solid/multicystic subtype (P < 0.05). WIP, an upstream regulator of N-WASP, and F-actin were significantly upregulated along the tumour invasive front compared to tumour centres (P < 0.05). Except for males with cortactin overexpression, other clinical parameters (age, ethnicity and anatomical site) showed no significant correlations.

CONCLUSIONS: Present results suggest that local invasiveness of ameloblastoma is dependent upon the migratory potential of its tumour cells as defined by their distribution of cortactin, N-WASP and WIP in correlation with F-actin cytoskeletal dynamics.

Clinicopathological study of peripheral odontogenic fibromas (WHO-type) in Malaysians (1967-95)

Siar CH, Ng KH

Br J Oral Maxillofac Surg, 2000 Feb;38(1):19-22.

PMID: 10783442

Analysis of case records of 46 patients with peripheral odontogenic fibroma (1967-95) diagnosed in the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, disclosed a relatively young age of onset (mean, 32.2 years; range 5 months-64 years; peak incidence second decade of life), a slight female preponderance (M:F ratio 1:1.3), no racial predilection, a slight bias towards location in the mandible (52%) and a wide histomorphological range. All cases were treated by simple excision. Follow-up records were generally not available, so we do not know what the recurrence rate is.

An immunohistochemical study of the lining epithelium of odontogenic keratocyst

Siar CH, Ng KH

J Nihon Univ Sch Dent, 1995 Sep;37(3):163-9.

PMID: 7490610

The lining epithelium of 15 cases of odontogenic keratocyst (OKC) was evaluated immunohistochemically. The peroxidase-antiperoxidase technique was applied to study the distribution of polyclonal keratin and S-100 protein while the indirect method was used to examine monoclonal vimentin and desmin reactivity. Consistent positive keratin staining was revealed in the lining epithelium of all 15 OKCs with additional intense staining in the stratum corneum. None of the cases showed vimentin or desmin reactivity within the lining epithelium elements. One of the 15 cysts studied showed positive S-100 protein staining in the nuclei of the lining epithelial cells. The pertinent literature on the immunophenotyping of the lining epithelium of OKC is reviewed.

Denture hyperplasia and oncocytic metaplasia

Siar CH, Ng KH, Ngui CH

Ann Dent, 1992;51(1):27-8.

PMID: 1632623

A case of denture hyperplasia of the upper labial sulcus with concomitant oncocytic metaplastic changes is described. The patient concerned is an elderly male wearing an ill-fitting upper full denture.

'Combined ameloblastoma and odontogenic keratocyst' or 'keratinising ameloblastoma'

Siar CH, Ng KH

Br J Oral Maxillofac Surg, 1993 Jun;31(3):183-6.

PMID: 7685634

Four cases of either combined occurrence of ameloblastoma and odontogenic keratocyst or a rare keratinising variant of ameloblastoma are presented. The cardinal histomorphologic characteristics are simultaneous occurrence of ameloblastomatous epithelial islands with central keratinisation and multiple keratinising cysts. Immunohistochemically the tumour elements were keratin positive and occasionally S-100 protein and desmin positive. Major differential diagnosis of these neoplasms are discussed.

Unusual granular cell odontogenic tumor. Report of two undescribed cases with features of granular cell ameloblastoma and plexiform granular cell odontogenic tumor

Siar CH, Ng KH

J Nihon Univ Sch Dent, 1993 Jun;35(2):134-8.

PMID: 7692017

Granular cell ameloblastoma (GCA) is a well recognized variant of follicular ameloblastoma with extensive granular cell change. In contrast, plexiform granular cell odontogenic tumor (PGCOT) is a rare and recently described lesion characterized histologically by a monophasic plexiform pattern of granular cells. In this paper, two cases of an unusual granular cell odontogenic tumor exhibiting combined features of these two entities are described along with their immunohistochemical characteristics. The granular cells of both the GCA and PGCOT areas showed similar patterns of expression for keratin and S-100, which differed from those of typical ameloblastoma. No reactivity for desmin or vimentin was noted. The histomorphologic and immunohistochemical features of these hybrid tumors suggest that the granular cells present have a common origin, most probably the odontogenic epithelium.

Patterns of expression of intermediate filaments and S-100 protein in desmoplastic ameloblastoma

Siar CH, Ng KH

J Nihon Univ Sch Dent, 1993 Jun;35(2):104-8.

PMID: 7692015

Seventeen cases of desmoplastic ameloblastoma were examined immunohistochemically. Immunoperoxidase techniques were applied for detection of keratin, desmin, vimentin and S-100 protein expression in these tumors. The tumor epithelium of desmoplastic ameloblastoma exhibited weak, focal, inconstant keratin staining, weak, variable expression of S-100 protein, desmin immunoreactivity of mild to moderate intensity and vimentin non-reactivity. The pertinent literature on the immunohistochemistry of ameloblastomas is briefly reviewed.

Ameloblastoma in Malaysia--a 25-year review

Siar CH, Ng KH

Ann Acad Med Singap, 1993 Nov;22(6):856-60.

PMID: 8129343

Four hundred and one cases of ameloblastoma of the jaw diagnosed in the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, between 1967 and 1991 have been analysed. There were 214 males and 187 females. Of these, 50.1% were Malays, 34.7% Chinese, 8.2% Indians and 7.0% other races. Seventy-two percent of patients were in the second, third and fourth decades of life (mean age: 30.8 years). Ninety-three percent of tumours occurred in the mandible and 6.5% in the maxilla. There were 337 cases of conventional ameloblastoma, 49 cases of the unicystic variant and four cases of peripheral ameloblastoma. The predominant histologic patterns were plexiform (34.2%), follicular (16.5%) and mixture of both (17.7%). Majority of the cases were conservatively treated by enucleation. Fifty-nine cases presented with recurrences. Present findings were generally compatible with regional serial studies reported from Thailand, Singapore and Japan.

Peripheral odontogenic fibroma with clear cell odontogenic epithelium

Siar CH, NG KH

J N Z Soc Periodontol, 1995.

PMID: 9227094

The clinical and histological features of the peripheral odontogenic fibroma are briefly outlined. A case arising from the attached lingual gingiva between the mandibular right permanent first molar and the second molar in a 67 year old Indian female is reported here. The unusual occurrence of marked clear cell differentiation within the odontogenic epithelial component, and histogenetic link to the clear cell rests of the dental lamina and surface epithelium are discussed.

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