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Biomedical subjects

M Shear

Publications and source records attributed to M Shear.

At least 19 recordsLinked to original sources
PubMed1996

Age standardized incidence rates of oral cancer in South Africa, 1988-1991.

While numbers of papers on oral cancer in South Africa have been published, there have been very few studies on standardized morbidity rates. This paper has developed data collected by the National Cancer Registry from the entire country for the four year period 1988-1991 to present frequency, age standardized incidence rates (ASIRs) and life-time risk (LR) for histologically-diagnosed intra-oral cancers in female and male Asian, black, coloured and white South Africans. During this period 5396 cases of oral cancer were diagnosed in a total number of 157,307 cancer cases (3.4 per cent) excluding squamous cell carcinoma (SCC) and basal cell carcinoma (BSC) of the skin. Intra-oral cancer in all South African females and males accounted, respectively, for 1.8 per cent and 5.0 per cent of all cancers. There was a male preponderance in black, coloured and white groups but females were affected more frequently than men among Asians. The incidence in Asian women (6.66) was higher than those of the women in any of the other population groups, whereas the lowest incidence was found in black women (1.75). The incidence rate in coloured men was particularly high (13.13) whereas the incidence in white males (8.06) was not substantially lower than among black males (9.05). Differences between the eight groups were not significant (X2 = 6.24, df = 3, p > 0.1). The Cumulative Life Time Risk (LR) of developing intra-oral cancer for males and females in the four population groups ranged from 1:65 in coloured males to 1:455 for black females. Gender differences in LR in both black and coloured groups, signals substantial differences in exposure to known carcinogens for this disease. It is disturbing to note that the incidence in the period 1988-1991 was higher in Indian women that it was in 1964-1966, and that educative preventive measures have failed. Similarly, the incidence of intra-oral cancer in coloured men of 13.13 is substantially higher than the figure of 8.8 reported in 1979. If this is an accurately reflected trend, then a major educative programme needs to be pursued in this direction if the relative risk of one in 65 is to be reduced.

Adolescent↗
PubMed1995

Vacuolated cells and mucous metaplasia in the epithelial linings of radicular and residual cysts.

The purpose of this study was to determine whether a consistent association exists between mucous cells and clear or vacuolated cells in the epithelial lining of radicular and residual cysts and to consider whether the vacuolated cells may represent a stage in the histogenesis of mucous metaplasia in these linings. Single sections from each of 154 mandibular radicular and residual cysts were stained with periodic acid-Schiff (PAS) after diastase digestion. Fifteen cases which showed mucous metaplasia were included in the study and were examined for the presence of vacuolated cells associated with the mucous cells. Mucous cells were present singly or in groups within all layers of the stratified squamous epithelial lining except the basal cell layer. In nearly all instances small to large ovoid vacuolated cells were found closely associated with the mucous cells. Occasional vacuolated cells contained sparse mucin granules or a delicate network of PAS-positive, diastase-resistant material. It is suggested that the clear cells may represent a stage in the histogenesis of mucous metaplasia.

Epithelium↗
PubMed1994

Developmental odontogenic cysts. An update.

This review paper reports recent advances in the subject of developmental odontogenic cysts, essentially those of the past decade, starting with reference to the new WHO classification (1). On keratocysts, the latest reported recurrence rates are assessed as are their mode of growth, immunocytochemistry, immunology, genetic studies, and work on specific keratocyst antigens. There is a critical account of the group of lesions which includes the gingival cyst of adults, lateral periodontal cyst, botryoid odontogenic cyst and glandular odontogenic cyst, and their possible relationship to one another. On dentigerous cysts, reference is made to the relationship between them and deciduous teeth, as well as to their immunocytochemistry and immunology. Recent work on the unicystic ameloblastomas, their classification and prognosis, is assessed, as is the calcifying odontogenic cyst and its relationship with solid odontogenic tumours.

Ameloblastoma↗
PubMed1993

Epidemiology of diarrhoeal illness associated with coccidian-like organism among travellers and foreign residents in Nepal.

A newly described organism called CLB (coccidian-like or cyanobacterium-like body) has been identified in cases of prolonged diarrhoea. To confirm an association of CLB with disease and identify risk factors for transmission, we conducted a case-control study of travellers and foreign residents at two outpatient clinics in Kathmandu, Nepal. Patients without diarrhoea were matched to CLB cases by clinic and date of visit. For comparison, patients with other causes of diarrhoea were also studied. Stools were examined for enteric pathogens with standard microbiological and molecular genetic techniques. CLB was identified in 108 (11%) of 964 individuals with gastrointestinal symptoms compared with only 1 (1%) of 96 symptom-free controls (p = 0.003). 7% of residents in the US Embassy community acquired the infection. The diarrhoeal illness associated with CLB lasted a median of 7 weeks (interquartile range 4-9) compared with 9 days (4-19) for individuals with other causes of diarrhoea (p < 0.0001). The prevalence of other enteric pathogens was no higher among CLB cases than among symptom-free controls. Patients with CLB infection were more likely than controls to report consumption of untreated water (odds ratio 3.98; 95% CI 1.29-13.14); organisms of the same appearance were identified in an epidemiologically implicated water sample. The significant association of CLB with prolonged diarrhoea, and the low rate of other enteropathogens in CLB cases, strongly supports the hypothesis that CLB is a new pathogen. Epidemiological and environmental data suggest that the organism is waterborne.

Adolescent↗
PubMed1992

The WHO Histological Typing of Odontogenic Tumours. A commentary on the Second Edition.

This article introduces the revised World Health Organization (WHO) classification of odontogenic tumors and jaw cysts and certain bone lesions that either are peculiar to the jaws or have distinctive features in that location. The new and revised classification is compared with the previous version, the reasons for the changes are outlined, and reference is made to a number of newly characterized lesions that have been included.

Bone Neoplasms↗
PubMed1992

The lateral periodontal cyst: an update.

Lateral periodontal cysts account for 0.8% of all jaw cysts seen in our department. Published reports have indicated that they occur most frequently in the 5th to 7th decades, that there is a male preponderance and that they are located mainly in the mandibular canine-premolar region. In our own series of 20 cases, 10 were found in the anterior maxilla. We have distinguished unicystic and multicystic (including botryoid) varieties. They were lined predominantly or exclusively by thin reduced enamel epithelium-like tissue which contained many clear cells and epithelial thickenings referred to as plaques. Glycogen was present in the epithelium of two-thirds of our cases although not exclusively in the clear cells, many of which showed no positivity. Two of our examples of the botryoid variety were different histologically, being lined predominantly by non-keratinizing stratified squamous epithelium with crowded and pyknotic nuclei and no clear cells. One case contained melanin while another showed epithelial crypt formation and superficial palisaded low columnar cells as seen in the glandular odontogenic cyst. This raised the question of whether the latter may form part of the clinicopathologic spectrum of lateral periodontal cyst. The histogenesis of lateral periodontal cysts is uncertain but we favour origin from reduced enamel epithelium.

Adult↗
PubMed1992

Gingival cyst in adults.

A retrospective study is reported of 14 cases of gingival cyst of adults. Clinical data were pooled with well-documented cases in the literature. Most cases occurred in the 5th and 6th decades and in the premolar-canine-incisor area. Microscopically, the epithelial lining ranged from a thin, flat to cuboidal layer, 1-3 cells thick, resembling reduced enamel epithelium, to a nonkeratinized stratified squamous epithelium without rete ridges, of about 5-6 layers. Epithelial cells were frequently atrophic and this could involve the full thickness of the epithelium leaving an amorphous band of eosinophilic material. Plaque-like epithelial thickenings are sometimes present. Multicystic or "botryoid" forms may occur. The cysts are of developmental origin, arising either from basal cell extensions of overlying epithelium; or from postfunctional odontogenic epithelial residues of the dental lamina or rests of Malassez; or from junctional epithelium in the gingival crevice. The latter theory of origin is favored.

Adolescent↗
PubMed1988

The unicystic ameloblastoma: a clinicopathological study of 57 cases.

A clinicopathological study of 57 unicystic ameloblastomas has been undertaken, which represents 15% of all cases of ameloblastoma accessioned in our department over a 30-yr period. Of the cases where gender was recorded: 30 were male and 23 female. The majority of patients were black (51 cases) and most occurred in the mandible (52). This distribution conforms to that of solid and multicystic ameloblastomas. The mean age at diagnosis was 23.8 years (S.D. 14.9) which is significantly younger than for the conventional counterpart (p less than 0.1%). The lesions were classified histologically into 3 groups: Group 1 (42%) cyst lined by a variable often non-descript epithelium; Group 2 (9%) cyst showing intraluminal plexiform proliferation of epithelium; Group 3 (49%) cyst with invasion of epithelium into the cyst wall in either follicular or plexiform patterns. While Group 1 and 2 lesions may be treated by enucleation, Group 3 lesions should be treated aggressively as for conventional ameloblastomas. The objectives of correct histological diagnosis, subclassification and appropriate therapy are best achieved by enucleation biopsy. There is little evidence to support origin from pre-existing odontogenic cysts.

Adolescent↗
PubMed1985

Radicular cysts arising from deciduous teeth. Review of the literature and report of 23 cases.

Radicular cysts arising from deciduous teeth are rare. 28 such cases have been recorded in the literature since 1898. In this study, we present 23 personally-observed cases of radicular cysts arising from deciduous teeth. The patients' ages ranged from 4 to 12 years with one exceptional case aged 19 years. The M:F ratio was 1.6:1. The mandible was affected more frequently than the maxilla and the deciduous molars were the teeth most commonly involved. 2 of the cysts presented multi-locular radiolucency; in 9 cases, buccal expansion was noticed and in 8 cases, permanent buds were displaced. Caries was the most common etiologic factor in the formation of the cysts. Histologically, cysts in varying stages of development were lined by proliferating non-keratinized stratified squamous epithelium.

Child↗
PubMed1985

A critical evaluation of epithelial dysplasia in oral mucosal lesions using the Smith-Pindborg method of standardization.

Standardization is one of the greatest problems in assessing epithelial dysplasia, as is establishing the relative importance of different clinical and dysplastic features. In this study, 214 cases characterized histologically by varying degrees of epithelial dysplasia, were analyzed for various clinical features: and representative sections were assessed histologically and graded according to the Smith-Pindborg standardized scoring system. Data were analyzed by computer. Seven cases with scores of less than 10 were excluded as not dysplastic. There were 85 cases (41%) with scores of 11-25 which were regarded as mild dysplasia; 60 (29%) with scores of 26-45 were regarded as moderate dysplasia; and 62 (30%) with scores of more than 45 which were reported as severe dysplasia. Peak frequency was in the 6th decade and the severe dysplasias were most frequent in the 8th decade. The M:F was 2:1. Tongue (58 cases), lower lip (36), floor of mouth (32) and cheeks (26) were sites most commonly involved. Of 107 cases, 93 were described as homogeneous leukoplakia, 11 as speckled leukoplakia and 3 as erythroplakia. The distribution of mild, moderate and severe dysplasias did not differ significantly by age, sex or race. Half of all cases involving floor of mouth and oropharynx were severely dysplastic, whereas most lesions occurring in cheek and alveolar mucosa/gingiva were mildly dysplastic; but differences were not significantly different. Severe grades of each dysplastic feature, as might be expected, occurred in lesions classified finally as 'severe dysplasia'.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Epithelial dysplasia immediately adjacent to oral squamous cell carcinomas.

A number of workers have attempted to identify dysplastic features which may be predictors of malignant change, by prospective studies of dysplastic lesions. In the present study we have looked at dysplastic changes immediately adjacent to established squamous carcinomas in an attempt to determine whether any predictors can be identified in this way. Eighty cases were included in the study for whom information on tobacco usage was known. Clinical details were recorded. Histological features in epithelium immediately adjacent to the carcinoma were studied in representative sections. Eighteen specific histological characteristics were noted as present or absent. Data were transferred by Conversational Monitoring System (CMS) terminal, processed and analyzed by the Statistical Analysis System (SAS) Computer package. Only 8 patients were non-smokers (10%). Dysplastic changes in adjacent epithelium were frequently multicentric. Changes appear to occur first in the basal layer in the form of disturbance of polarity or basal cell hyperplasia, while other dysplastic features are absent. The feature referred to as basal cell hyperplasia appears, in fact, to represent disturbed epithelial maturation. In 80% of cases increased nucleo-cytoplasmic ratio appears to result from a decrease in cytoplasmic volume rather than increased nuclear size. A defect in RNA synthesis may be a factor. A sharp decrease in inflammatory cells in the lamina propria of adjacent epithelium, compared with that of the carcinoma, was observed. Russell bodies were noted in 5 of the 8 lesions in non-smokers (63%) and in 16 of 72 lesions in smokers (22%) (p less than 0.001; Chi2 17.65).

Adult↗
PubMed1984

Aneurysmal bone cyst of the jaws. (I). Clinicopathological features.

A clinicopathological study has been performed on a series of 42 well-documented examples of aneurysmal bone cyst of the jaws recorded in the literature, and 4 additional personally observed cases. Most occurred in the first three decades (93%), 2/3 of patients being younger than 20 years. There was a preponderance of females (62%). Both mandible and maxilla were involved, particularly the molar regions. A number of mandibular cases extended to the angle and ascending ramus. Swelling was usually present and there was frequently a history of rapid growth. Radiologically, they often appeared as multilocular radiolucencies with expansion and thinning of the cortical plates. Histologically, the lesions consisted of multiple cystic spaces of varying size, usually filled with blood. The intervening solid tissue frequently showed features of other pathological lesions, particularly the central giant cell granuloma, but occasionally as fibrous dysplasia, ossifying fibroma and cementifying fibroma. Recurrences have been common probably because of technical difficulties in entirely removing very large lesions. Thorough curettage, if necessary by an extraoral approach, is the most favoured method of treatment.

Adolescent↗