Displaying publications 21 - 40 of 91 in total

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  1. Ong AH, Siar CH
    Aust Dent J, 1998 Aug;43(4):229-33.
    PMID: 9775467
    The cemento-ossifying fibroma is classified as an osteogenic neoplasm of the jaws. It commonly presents as a progressively growing lesion that can attain an enormous size with resultant deformity if left untreated. A case of a large cemento-ossifying fibroma involving the left mandible is described in a 15 year old male patient. The clinical, radiographic and histological features as well as surgical findings are presented. The treatment of choice of this lesion is also emphasized. Two years after surgery, there was no evidence of recurrence and the transosseous wire used to immobilize the fracture was found to be completely buried in the jaw bone.
  2. Ong ST, Siar CH
    Aust Dent J, 1997 Dec;42(6):404-8.
    PMID: 9470284
    Florid cemento-osseous dysplasia refers to a group of fibro-osseous lesions which are exuberant, multiquadrant and arise from the tooth-bearing area of the jaws. It is classically described as a condition occurring almost exclusively in middle-aged black women. A case of florid cemento-osseous dysplasia occurring in a young Chinese male is reported which was rare in regard to race and sex. This 20 year old Chinese man presented with huge symmetrical bony lesions in all four quadrants of the jaws. Clinical presentation, radiological findings and histological features of the excised specimens are described. Treatment of the lesions was unusual. Curettage was first done with minimal benefit and it was followed by mandibular recontouring to improve facial appearance. The outcome of these procedures will be discussed.
  3. Ng KH, Siar CH
    J Nihon Univ Sch Dent, 1997 Dec;39(4):171-5.
    PMID: 9476429
    This report reviews the clinicopathologic characteristics of 104 cases of odontomas diagnosed in the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, over a 29-year period (1967-1995). The results showed no real predilection in terms of sex (M:F ratio, 1:1), race (45.2% Malays, 40.4% Chinese, 10.6% Indians and 3.8% other races) or site (maxilla:mandible ratio, 1: 1.04) distribution. The mean age at presentation was 24.8 years and the age range was 3-74 years. There were 102 intraosseous and 2 extraosseous odontomas. Swelling was the most common presenting complaint. The majority of cases (81.9%) were clinically diagnosed as odontomas. The treatment of choice was surgical enucleation. Compound (43.3%) and complex (35.5%) odontomas were the two most common histological types encountered. The present findings correlate favorably with reported studies from other geographic areas.
  4. Ng KH, Siar CH
    J Laryngol Otol, 1996 Aug;110(8):757-62.
    PMID: 8869610
    We reviewed the clinicopathological characteristics of 13 cases of calcifying epithelial odontogenic tumour (CEOT) (Pindborg tumour) diagnosed in the Division on Stomatology, Institute for Medical Research, Kuala Lumpur, over a 29-year period. There were eight female and five male patients. These consisted of eight (61.5 per cent) Malays, three (23.1 per cent) Chinese, one (7.7 per cent) Indian and one (7.7 per cent) Melanau. Their ages at presentation ranged from 19-61 years (mean age, 31.8 years). There were 12 central and one peripheral CEOT. Of these, 76.9 per cent of cases were located in the maxilla, the remaining in the mandible. The commonest clinical diagnosis was a dentigerous cyst (66.7 per cent). Enucleation was the main mode of treatment. Histologically, sheets and strands of polyhedral epithelial cells containing eosinophilic, homogeneous globules with Liesegang rings were observed. One case also showed extensive calcification and clear cell differentiation. Immunohistochemistry revealed a variable keratin staining of the CEOT epithelium, confirming its heterogeneity.
  5. Siar CH, Ng KH
    J Nihon Univ Sch Dent, 1992 Jun;34(2):96-105.
    PMID: 1380072
    Twelve pleomorphic adenomas of minor salivary gland origin were examined for the distribution of S-100 protein, detected using the peroxidase-antiperoxidase (PAP) method. Strong S-100 protein immunoreactivity was noted in areas containing plasmacytoid cells, stellate and spindle cells against a myxochondroid or hyalinous stroma, and solid epithelial areas. Tubular and duct-like structures showed variable stainability. Stromal tissue and normal salivary glands were generally negative for S-100 protein. These findings were compared with those reported elsewhere.
  6. Siar CH, Ng KH
    Br J Oral Maxillofac Surg, 1988 Jun;26(3):215-20.
    PMID: 2456095
    The records of the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, Malaysia, were reviewed for the incidence of odontogenic keratocysts of the orthokeratinised variety, during the 20-year-period, 1967 to 1986. Nine cases were found. The clinical, histological and radiological features of these cases are reported. Many features were similar to previous reports of this entity but a peak incidence in the second decade of life, an almost even distribution in the maxilla and mandible, and a distinct predilection for the Chinese were observed. It is suggested that these features may be peculiar to Malaysians.
  7. Siar CH, Ng KH
    Br J Oral Maxillofac Surg, 1991 Apr;29(2):106-9.
    PMID: 2049349
    The combined epithelial odontogenic tumour represents a hybrid lesion comprising primarily areas of adenomatoid odontogenic tumour intermixed with foci of calcifying epithelial odontogenic tumour. Five such cases retrieved from the files of the Division of Stomatology, Institute for Medical Research, Kuala Lumpur, and four others from the existing literature were analysed. A mean age of 18.8 years, a female preponderance (66.7%) with a male to female ratio of 1:2 and predilection for the mandible (55.6%) were observed. All cases were treated by conservative surgery and the lack of recurrence confirmed the innocuous nature of this lesion.
  8. Ng KH, Siar CH
    Oral Surg. Oral Med. Oral Pathol., 1990 Aug;70(2):210-3.
    PMID: 2290651
    This report details a case of mandibular peripheral ameloblastoma having a clear cell component. The latter consisted of ovoid cells with vacuolated or clear cytoplasm and vesicular or pyknotic nuclei that may be disposed as discrete clusters or show direct transition from typical acanthomatous areas. Comparison of this lesion with other odontogenic and nonodontogenic tumors that contain clear cells is discussed in the context of the differential diagnosis.
  9. Ng KH, Siar CH
    Singapore Dent J, 1989 Dec;14(1):42-5.
    PMID: 2487475
    Mucoepidermoid tumours of the minor salivary glands of the tongue are rarely encountered. A case of a high-grade malignant type is reported here. Merits of subdivision of the mucoepidermoid tumour on the basis of its malignant potential are outlined, and variations of histological presentation of the present tumour at its primary and nodal sites are discussed.
  10. Siar CH, Ng KH
    J Laryngol Otol, 1991 Nov;105(11):971-2.
    PMID: 1722237
    A case is described of ameloblastoma of maxilla presenting with numerous calcified keratin pearls. The significance of cellular variation in relation to the behavioural potential of the ameloblastoma in general is briefly discussed.
  11. Siar CH, Foo GC
    Med J Malaysia, 1984 Dec;39(4):306-10.
    PMID: 6544939
    Toxoplasmosis is a parasitic infection of worldwide distribution. It is caused by an obligate intracellular parasite, Toxoplasma gondii. The commonest form of this disease is the acquired simple lymphadenopathy. Such a case is described and the clinicopathological significance of the disease is discussed.
  12. Ng KH, Siar CH
    Med J Malaysia, 1986 Sep;41(3):213-9.
    PMID: 2444865
    The morphology, incidence and distribution of hyaline cells in ten cases each of pleomorphic adenoma, adenoid cystic carcinoma, adenocarcinoma and mucoepidermoid tumour were studied by conventional light microscopy. Results showed that the hyaline cells were identified in 60% of pleomorphic adenoma and in 20% of mucoepidermoid tumours, but were absent in adenoid cystic carcinoma and adenocarcinoma. Relative area estimation of hyaline cells in pleomorphic adenomas showed that this may range from 2.2% to 30.4% of the total tumour area. The usefulness of the hyaline cell as a diagnostic criteria in distinguishing between some of the salivary gland tumours was also discussed.
  13. Siar CH, Ng KH
    Pathology, 2019 Aug;51(5):494-501.
    PMID: 31262562 DOI: 10.1016/j.pathol.2019.04.004
    The ameloblastoma is the most common and clinically significant odontogenic epithelial neoplasm known for its locally-invasive behaviour and high recurrence risk. Epithelial-to-mesenchymal transition (EMT) is a fundamental process whereby epithelial cells lose their epithelial characteristics and gain mesenchymal properties. EMT induction via transcription repression has been investigated in ameloblastoma. However, morphologically evident mesenchymal phenotypic transition remains ill-defined. To determine this, 24 unicystic (UA), 34 solid/multicystic (SA) and 18 recurrent ameloblastoma (RA) were immunohistochemically examined for three EMT-related mesenchymal markers, alpha smooth muscle actin (α-SMA), osteonectin and neuronal cadherin (N-cadherin). All three factors were heterogeneously detected in ameloblastoma samples (α-SMA, n=71/76, 93.4%; osteonectin, n=72/76, 94.7%; N-cadherin, n=24/76, 31.6%). In the tumoural parenchyma, immunoreactive cells were not morphologically distinct from their non-reactive cellular counterparts. Rather, α-SMA and osteonectin predominantly labelled the cytoplasm of central polyhedral > peripheral columnar/cuboidal tumour cells. N-cadherin demonstrated weak-to-moderate circumferential membranous staining in both neoplastic cell types and cytoplasmic expression in spindle-celled epithelium of desmoplastic amelobastoma. For all tumour subsets, α-SMA and osteonectin scored significantly higher in the stroma > parenchyma whilst α-SMA was overexpressed along the tumour invasive front > centre (p<0.05). Stromal N-cadherin scored higher in SA > UA and RA > UA (p<0.05). Other clinicopathological parameters showed no significant associations. Taken together, acquisition of mesenchymal traits without morphologically evident mesenchymal alteration suggests partial EMT in ameloblastoma. Stromal upregulation of these proteins in SA and RA implicates a role in local invasiveness.
  14. Kechik KA, Siar CH
    Ann Diagn Pathol, 2018 Feb;32:17-22.
    PMID: 29414392 DOI: 10.1016/j.anndiagpath.2017.08.002
    BACKGROUND AND AIMS: The odontogenic keratocyst (OKC) remains the most challenging jaw cyst to treat because of its locally-aggressive behaviour and high recurrence potential. Emerging evidence suggests that osteopontin, its receptors CD44v6 and integrin αv, and podoplanin, have a role in the local invasiveness of this cyst. However the spatial distribution characteristics of these pro-invasive markers in the lining epithelium of OKC, and their association with the clinicopathologic parameters of OKC are largely unexplored. This study sought to address these issues in comparison with dentigerous cysts (DCs) and radicular cysts (RCs) and to evaluate their biological relevance.

    METHODS: A sample consisting of 20 OKC cases, 10 DCs and 10 RCs was subjected to immunohistochemical staining for osteopontin, CD44v6 and integrin αv, and podoplanin, and semiquantitative analysis was performed.

    RESULTS: All factors (except integrin αv) were detected heterogeneously in the constitutive layers of the lining epithelium in all three cyst types. Key observations were significant upregulation of CD44v6 and podoplanin in OKC compared to DCs and RCs, suggesting that these protein molecules may play crucial roles in promoting local invasiveness in OKC (P<0.05). Osteopontin underexpression and distribution patterns were indistinctive among all three cysts indicating its limited role as pro-invasive factor. Clinical parameters showed no significant correlations with all protein factors investigated.

    CONCLUSIONS: Present findings suggest that an osteopontinlow CD44v6high and podoplaninhigh immunoprofile most probably represent epithelial signatures of OKC and are markers of local invasiveness in this cyst.

  15. 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.
  16. 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.
  17. Siar CH, Mah MC, Gill PP
    Eur Arch Otorhinolaryngol, 2012 Mar;269(3):999-1004.
    PMID: 21789676 DOI: 10.1007/s00405-011-1712-x
    Early detection of oral potentially malignant epithelial lesions (PMELs) is aimed at improving survival rates as carcinogenesis is a multistep process and prevention is possible if these lesions are detected at an early and reversible stage of the disease. A prospective clinical study aimed at determining the prevalence of bilateral 'mirror-image' oral PMELs was carried out. Sample consisted of 32 (53.3%) Indians, 23 (38.3%) Chinese, 4 (6.7%) Malays and one (1.7%) Nepalese. All had histopathological confirmation of their primary existing PMEL as inclusion criteria. A total of 70 primary lesions were detected. The most common PMEL found was oral lichen planus. Of these, 28 (46.7%) patients exhibited bilateral 'mirror-image' lesions (n = 42) either synchronously (n = 32/42) or metachronously (n = 10/42). The remaining 32 (53.3%) patients had normal-looking contralateral mucosa. Present findings suggest that patients presenting with oral PMELs are at greater risk of developing a second lesion, most probably in the contralateral 'mirror-image' site.
  18. Siar CH, Mah MC, Gill PP
    Asian Pac J Cancer Prev, 2011;12(3):631-5.
    PMID: 21627356
    BACKGROUND: It is known that abnormal changes may occur in any part of the oral mucous membrane exposed to a carcinogen. Therefore patients with oral potentially malignant disorders (PMDs) are at risk of developing similar lesions at multiple sites.

    OBJECTIVES: To determine the risk of the contralateral mucosa in patients presenting with oral PMDs.

    MATERIALS AND METHODS: Sixty individuals with PMDs were selected for this study. These comprised 32 (53.3%) Indians, 23 (38.3%) Chinese, four (6.7%) Malays and one (1.7%) Nepalese. All selected cases had histopathological confirmation of their primary existing lesion as inclusion criteria. Cases that subsequently presented with a lesion in the corresponding anatomical site also underwent scalpel incisional biopsy on this second lesion to verify its diagnosis. The remaining cases that presented with unilateral PMDs at the time of study were subjected to a cytobrush biopsy on the normal looking contralateral mucosa.

    RESULTS: A total of 70 primary PMDs were detected in 60 patients. The most common PMD found was oral lichen planus (n=40, 57.1%). Of the 60 patients studied, 28 (46.6%) exhibited bilateral lesions either synchronously (n=21, 35.0%) or metachronously (n=7, 11.6%). The remaining cases that had undergone cytobrush biopsy on the corresponding anatomical site yielded normal cytological results.

    CONCLUSIONS: Present findings demonstrated that patients presenting with PMDs in the upper aerodigestive tract are at a greater risk of developing a second lesion most probably in the contralateral anatomical site.

  19. 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.
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