Displaying all 15 publications

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  1. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  2. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  3. Siar CH, Ong ST, Ng KH
    Singapore Dent J, 1996 Jul;21(1):19-22.
    PMID: 10597178
    Adenomatoid odontogenic tumours (AOT) are benign, hamartomatous odontogenic lesions that not uncommonly mimic a dentigerous cyst radiographically. Such a case as found involving an unerupted left maxillary canine in a 19-year-old Chinese female is described. The differential diagnosis of some common odontogenic cysts and neoplasms occurring in Malaysians, that may present in a dentigerous relationship to an unerupted tooth is discussed. A brief review of the radiographic literature on AOT is also included.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  4. Siar CH, Ng KH
    J Laryngol Otol, 1994 Mar;108(3):269-71.
    PMID: 8169519
    A case is described of ameloblastoma of the mandible presenting with multiple recurrences and subsequent extension to the maxilla with resultant transformation into an aggressive (malignant?) epithelial odontogenic ghost cell tumour. The latter is a rare, biologically virulent entity that affects mainly males, exhibits a preference for the maxilla and is histologically characterized by atypical malignant odontogenic epithelium associated with areas of ghost cell formation and varying amounts of dentinoid.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  5. Ng KH, Siar CH
    Br J Oral Maxillofac Surg, 1993 Oct;31(5):299-303.
    PMID: 8218083
    Seventeen cases are reported of desmoplastic variant of ameloblastoma of the jaws observed during the years 1967-1991. There were 12 females and 5 males, and these consisted of 7 Chinese, 6 Malays, 2 Indians, 1 Sikh and 1 Kadazan. Their ages at diagnosis ranged from 21-60 years with a mean of 36.6 years. There were 10 mandibular and 7 maxillary tumours. Of these, 14 cases involved the anterior segment with extension to the premolar region in 5 cases. 60% of cases were radiologically suggestive of fibro-osseous lesions. The main mode of treatment was resection and 1 case presented with recurrence. The findings of this study were compared with those of previous reports.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  6. Rengaswamy V
    Br J Oral Surg, 1977 Nov;15(2):160-5.
    PMID: 271018
    A study was made of the clinical statistics of odontogenic cysts treated at two hospitals in West Malaysia over a 6-year period. The general incidence of the individual cyst-types is similar to that reported in previous studies. A marked difference in the age distribution of radicular cysts emerged and 80% of the residual cysts in the survey occurred amongst the Chinese population. Reasons for the distribution variation are discussed.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  7. Sivapathasundharam B, Einstein A, Syed RI
    Indian J Dent Res, 2007 10 17;18(4):218-21.
    PMID: 17938502
    In the recent World Health Organization classification of odontogenic tumours, desmoplastic ameloblastoma has been characterized as a variant of ameloblastoma, with specific clinical, radiographical, and histological features. Till date, 145 cases have been reported in Japanese, Chinese, Malaysian, Western, and African populations, with very few cases described in Indians. Here, we report five cases in the Indian population. The male to female ratio was 3:2. The mean age at diagnosis was 33.2 years. Four of the tumours were located in the maxilla, in the anterior premolar region. The lone mandibular tumour was located anteriorly, crossing the midline. Three of the tumours had a mixed radiologic appearance with poorly defined borders. Unilocular change was seen in one of them. Two tumours presented as unilocular radiolucencies with specks of radiopacities and well-circumscribed borders. Histologically, irregular odontogenic islands, with a stretched-out 'kite-tail' appearance, were seen in a dense desmoplastic stroma. The peripheral layer of the epithelial islands was made up of flattened cells and the inner core was made up of spindle-shaped and, in some instances, squamous-shaped cells. In two cases, odontogenic epithelium in the form of follicles, typical of solid/multicystic ameloblastoma, was seen and these were typed as 'hybrid' variants. All the cases were treated by resection.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  8. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  9. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  10. Ramanathan K, Chelvanayagam PI, Ng KH, Ramanathan J
    Med J Malaysia, 1982 Mar;37(1):18-24.
    PMID: 7121342
    Ameloblastomas formed 1.1 percent of all oral pathology cases reported. The race, sex and age group distribution of 133 cases are shown. The peak age incidence (70.6 percent) was between 11-40 years. The mandible was involved 9 times more commonly than the maxilla. The anatomical sites of distribution, clinical and radiological features, histological variants and their correlation are discussed. Twenty two patients (15 percent) had ameloblastomas associated with a dentigerous cyst and/or unerupted teeth. Ameloblastomas with the above clinical features represented a much less aggressive form of neoplasm. The authors could not correlate histological variants of ameloblastoma with recurrence rates. The various treatment methods and the respective recurrence rates are outlined. Radiotherapy and marsupialization as treatment of ameloblastoma are not recommended. The indications for enucleation curettage, resection en bloc, segmental resection and hemimandibulectomy
    are emphasized. Ameloblastomas involving the maxilla should be treated by complete removal en bloc with a margin of normal tissue. Since ameloblastoma has the capacity to recur after several years of apparent cure patients who have been treated for ameloblastoma must be followed up periodically during their life time. So far no case of ameloblastoma in this study has shown evidence
    ofmetastasis.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  11. Al-Shaham AA, Samher AA
    J Plast Surg Hand Surg, 2010 Dec;44(6):318-21.
    PMID: 21446812 DOI: 10.3109/02844311003683713
    Despite the fact that cemento-ossifying fibromas of the maxilla may be quite large and locally aggressive, en-bloc excision is achieved by gentle blunt dissection, with the whole tumour mass peeled out from the adjacent structures. Until recently different fibro-osseous tumours that contained cementum were classified together as "cementomas". In 1992 The World Health Organization adopted a new classification that included these fibromas as benign osseous tumours. While such tumours of the mandible are common, those of the maxilla are rare. They are growth products of periodontal membrane remnant. The triggering mechanism in the formation of cementum outside the periodontal membrane remains unclear. We present a 35-year-old woman who had a giant expanding lobular mass in the right maxilla of 5 years duration. She had visual disturbances and nasal obstruction, and was treated successfully by surgical en-bloc resection of the tumour through an infraorbital transverse incision. The differential diagnosis included fibrous dysplasia, osteoid osteoma, osteoblastoma, chronic sclerosing osteomyelitis, ameloblastoma, squamous cell carcinoma of the maxillary sinus, calcifying epithelial odontogenic tumour (Pindborg tumour) and calcifying odontogenic cyst (Gorlin cyst). Histopathological examination confirmed a cemento-ossifying fibroma.
    Matched MeSH terms: Maxillary Neoplasms/pathology*
  12. Siar CH, Ha KO, Aung LO, Nakano K, Tsujigiwa H, Nagatsuka H, et al.
    Eur. J. Med. Res., 2010 Oct 25;15(10):456-60.
    PMID: 21156405
    BACKGROUND: notch receptors are critical determinants of cell fate in a variety of organisms. Notch signaling is involved in the chondrogenic specification of neural crest cells. Aberrant Notch activity has been implicated in numerous human diseases including cancers; however its role in chondrogenic tumors has not been clarified.

    METHOD: tissue samples from a case of primary chondrosarcoma of the maxilla and its recurrent tumor were examined immunohistochemically for Notch1-4 and their ligands (Jagged1, Jagged2 and Delta1) expression.

    RESULTS: both primary and recurrent tumors were histopathologically diagnosed as conventional hyaline chondrosarcoma (WHO Grade I). Hypercellular tumor areas strongly expressed Notch3 and Jagged1 in spindle and pleomorphic cells suggesting up-regulation of these protein molecules at sites of tumor proliferation. Expression patterns were distinct with some overlap. Differentiated malignant and atypical chondrocytes demonstrated variable expression levels of Jagged1, and weak to absent staining for Notch1, 4 and Delta1. Protein immunolocalization was largely membranous and cytoplasmic, sometimes outlining the lacunae of malignant chondrocytes. Hyaline cartilage demonstrated a diffuse or granular precipitation of Jagged1 suggesting presence of soluble Jagged1 activity at sites of abnormal chondrogenesis. No immunoreactivity for the other Notch members was observed. Calcified cartilage was consistently Notch-negative indicating down-regulation of Notch with cartilage maturation. Stromal components namely endothelial cells and fibroblasts variably expressed Notch1, 3 and Jagged1 but were mildly or non-reactive for the other members.

    CONCLUSIONS: Results indicate that Notch signaling pathway may participate in cellular differentiation and proliferation in chondrosarcoma. Findings implicate Notch3 and Jagged1 as key molecules that influence the differentiation and maturation of cells of chondrogenic lineage.

    Matched MeSH terms: Maxillary Neoplasms/pathology
  13. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  14. Siar CH, Nagatsuka H, Chuah KS, Rivera RS, Nakano K, Ng KH, et al.
    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.
    Matched MeSH terms: Maxillary Neoplasms/pathology
  15. 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.
    Matched MeSH terms: Maxillary Neoplasms/pathology
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