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Biomedical subjects

M Shear

Publications and source records attributed to M Shear.

At least 37 records · Page 2Linked to original sources
PubMed1984

Aneurysmal bone cyst of the jaws. (II). Pathogenesis.

The pathogenesis of the aneurysmal bone cyst is the subject of much controversy. This study was undertaken to test the hypothesis that the aneurysmal bone cyst is a secondary phenomenon which occurs in a primary lesion of bone. Histological material from 303 bone lesions was studied for evidence of development of aneurysmal bone cyst. Microcysts and blood-filled spaces, similar to those seen in aneurysmal bone cysts, were observed in 15 of 54 central giant cell granulomas studied (28%). The frequency was lower (10%) in 49 cases of fibrous dysplasia and very low in ossifying and cementifying fibromas. 1 of 7 cases of Paget's disease of bone showed large blood spaces. It is postulated that the initiating process of the aneurysmal bone cyst is the microcyst, which forms as a result of intercellular oedema in a primary lesion with loose, unsupported stroma. Rupture of vessels into the microcysts introduces blood under haemodynamic pressure. With little resistance provided by the stroma, the blood spaces resorb the surrounding bone and lift the periosteum, which produces a thin shell of new bone. Similar histological features were observed in 6 of 42 fibrosarcomas examined (14%) and in 8 of a series of 75 osteosarcomas (11%). While many of these lesions did not present with clinical similarity to the aneurysmal bone cyst, it is postulated that this type of case may account for the so-called malignant aneurysmal bone cyst occasionally reported.

Bone Cysts↗
PubMed1984

Fibrous histiocytomas of the oral and maxillofacial regions.

Fibrous histiocytomas of the oral and maxillofacial regions are rare. The present study analyzes a sample of 63 cases from the literature together with 7 personally observed cases. Age, sex, site, size, clinical behaviour, treatment and survival were evaluated and related to a histological classification based on that of Rosai (1981). Lesions were assessed for histological criteria which would place them in one of 2 groups: fibrous histiocytoma (FH) or pleomorphic fibrous histiocytoma (PFH). Within these 2 histological groups the cases were subdivided into clinically benign, aggressive or malignant lesions. Thirty-nine cases (56.0%) were classified as FH and 31 cases (44.0%) as PFH. The mean age of male patients with PFH was significantly higher than female patients with FH (t = 3.05; d.f. 37; p less than 0.0025). Lesions in the PFH group involved bone more frequently than those in the FH group (Yate's Chi2 = 16.66; d.f. 1; p less than 0.00025). Lesions involving bone for both histological groups were more likely to be aggressive or malignant than soft-tissue lesions (Yate's Chi2 = 29.9; d.f. 1; p less than 0.00025). Soft-tissue lesions were usually less than 5 cm in greatest diameter. Radiographic features of malignancy for lesions with bone involvement is of prognostic importance regardless of the histological appearance of the lesion. The majority of the lesions under study were from the deep tissues of the oral and maxillofacial regions.

Adolescent↗
PubMed1983

Intraoral salivary gland tumors: a retrospective study of 201 cases.

Two hundred and one cases of intraoral salivary gland tumors were studied from the files of the School of Pathology, University of the Witwaterstrand and South African Institute for Medical Research. 145 cases (72.5%) were classified as benign, comprising 140 pleomorphic adenomas and 5 monomorphic adenomas. The other 56 cases were classified as malignant or potentially malignant tumors, represented by 21 adenoid cystic carcinomas, 15 adenocarcinomas, 13 mucoepidermoid tumors, 5 carcinoma in pleomorphic adenomas and 2 epidermoid carcinomas. The patients in the malignant/potentially malignant group were significantly older than those in the benign group and a smaller proportion of their tumors were palatal, the difference being statistically significant. The high frequency of pleomorphic adenoma might result from a relatively higher number of black than white patients in this sample.

Adenocarcinoma↗
PubMed1981

Content and distribution of glycogen in oral epithelial dysplasia.

Forty-four oral lesions with epithelial dysplasia and 25 other benign and malignant lesions of the oral mucosa were examined after staining with hematoxylin-eosin and diastase controlled PAS. The intensity of the PAS-positivity for glycogen, the grade of dysplasia, the type of keratinization and the degree of subepithelial inflammation were recorded. Histologically normal epithelium at the margins of the lesions were used as controls. The presence and amount of glycogen in normal epithelium at the margins of the lesions were used as controls. The presence and amount of glycogen in normal epithelium at the margin of the lesions were used as controls. The presence and amount of glycogen in normal epithelium varied with the form of keratinization in that non- or parakeratinized epithelium was rich in glycogen whereas there was a negative glycogen-reaction in orthokeratinized epithelium. The most striking feature was an abrupt limitation of the glycogen at the junction between nondysplastic and dysplastic epithelium. The difference in the amount of glycogen in normal and dysplastic epithelium as assessed semiquantitatively, was statistically significant. There was no statistically significant difference in glycogen content with different degrees of dysplasia. The diastase controlled PAS-staining may therefore be a useful method of distinguishing dysplastic from nondysplastic epithelium in doubtful cases. Pseudoepitheliomatous hyperplastic epithelium covering granular cell myoblastoma did not contain any glycogen. Five of six squamous cell carcinomas and four verrucous carcinomas contained no demonstrable glycogen. Glycogen was present in the epithelium of the cases of lichen planus and "denture hyperplasia" investigated.

Adult↗
PubMed1981

Leukoplakia-like lesions developing in patients with oral discoid lupus erythematosus.

In a long-term follow-up of 52 patients with oral lesions of discoid lupus erythematosus (DLE) 8 patients showed a gradual transition of the typical DLE lesions to lesions which closely resemble leukoplakia. Histopathologically and immunopathologically the leukoplakia-like lesions generally showed features similar to those in leukoplakias not preceded by DLE. Ultrastructurally, the leukoplakia-like lesions showed the presence of cytoplasmic tubular structures in vascular endothelium in two out of three patients examined. The leukoplakia-like stage is considered to be an inactive or scar-like stage, which may be the mucous membrane counterpart of the atrophic scars following DLE lesions of the skin. A primary examination of a DLE patient presenting oral lesions at the leukoplakia-like stage may result in an incorrect diagnosis. Therefore, when investigating patients with leukoplakias, they should be questioned on previous or present skin lesions as well as symptoms of systemic lupus erythematosus.

Adult↗
PubMed1980

Verrucous hyperplasia of the oral mucosa.

Verrucous hyperplasia of the oral mucosa is a relatively unrecognized entity that may resemble verrucous carcinoma clinically and histologically. This study describes the clinical and histological features of the condition, particularly in relation to verrucous carcinoma. Sixty-eight cases were selected by screening all lesions accessioned as verrucous or papillary lesions of various kinds, dysplasias and leukoplakias. More cases occurred in women (56%) than in men (44%). All but 3 patients were 50 yr. or older, and 35% were over 70. Gingiva or alveolar mucosa were involved most frequently (27%), followed by cheek (24%), tongue (17%), floor of mouth and lip (12% each), and palate (8%). Verrucous processes are either sharp and heavily keratinized or blunt with a thin parakeratin layer. In 36 patients (53%), there was associated leukoplakia; in 20 (29%), there was associated verrucous carcinoma; in 45 (66%), associated epithelial dysplasia; and in 7, (10%) there was associated squamous carcinoma. Verrucous carcinoma or squamous carcinoma. Verrucous hyperplasia is best distinguished from verrucous carcinoma in biopsies taken at the margins of the lesions. In the former, the verrucous processes and the greater part of the hyperplastic epithelium are superficial to adjacent normal epithelium. In the latter, the verrucous processes are superficial, but the broad rete processes extend considerably deeper than adjacent normal epithelium, often pulling a margin of normal epithelium down with them into the underlying connective tissue.

Adult↗
PubMed1980

Dimensions of incisive fossae on dry skulls and radiographs.

The dimensions of the incisive fossae of 960 Negroid skulls were measured and the frequency of nasopalatine duct cysts in this material was determined. A random sample of 200 of the above skulls was radiographed under standardized conditions and the radiographic dimensions of the incisive fossae were compared statistically with their actual dimensions. Incisive fossa widths of greater than 6 mm were found in 148 specimens (15.3%), and anteroposterior dimensions of greater than 7 mm were found in 799 specimens (82.4%). Thirteen cysts were found. Radiographic measurements of incisive fossae were significantly different from those made on the skulls. Mean dimensions of the fossae in this sample were greater than those previously reported and there was a higher frequency of nasopalatine duct cysts.

Black People↗
PubMed1979

Microscopic changes in rat tongue following experimental cryosurgery.

Histological changes were studied in the rat tongue for varying periods of time up to 14 days following the application of a cryoprobe to the dorsal surface of rat tongue. Within minutes of the application, focal subepithelial vesiculation and hyperemia occurred. At 3 h there was evidence of damage to capillary walls, resulting in hemorrhage. Arterioles and venules were thrombosed and there were degenerative changes in the muscle layer of their walls. At 6 h ventral epithelium showed evidence of damage. At this stage vessel walls were pavemented with neutrophilic polymorphonuclear leukocytes (PMN) and some of the latter were seen in the vessel walls. At 24 h abundant PMN, many of them necrotic, were present in the vessel walls, apparently unable to pass through them. At 48 h numerous PMN were seen adhering to degenerating muscle fibers. By 4 days necrotic changes extended through the full thickness of the tongue, but concurrently it was observed that the larger thrombosed vessels were becoming recanalized. At 5 days repair by granulation tissue was taking place and at 6 days the vasculature was virtually reconstituted. By 14 days healing was complete.

Animals↗
PubMed1979

Basal cell extensions in human oral mucosa.

Basal cell extensions have frequently been observed in a variety of odontogenic lesions as well as in the fibrous epulis (fibrous hyperplasia of the gingiva). In order to determine the frequency of these extensions in normal human oral nucosa, a study using autopsy and surgical material was conducted. The results indicated that a specific type of rete ridge morphology exists for gingiva, including the presence of thin double stranded extensions which may be related to the functional role of the gingiva or to the fact that the odontogenic apparatus is derived from surface epithelium in this region in the developing embryo, or both. Similar extensions have not been found in other oral epithelia.

Gingiva↗
PubMed1978

Radiological features of mandibular primordial cysts. (Keratocysts).

Primordial cysts (keratocysts) have been shown to have a greater tendency to recurrence than other jaw cysts. Some radiological features may assist in establishing the diagnosis. Thirteen mandibular primordial cysts have been studied radiologically in detail. Characteristic features are extension along the medulla with minimal expansion except in young children. Margins are generally sharply demaracated and either smooth or scalloped. Cortical resorption occurs before expansion. The cysts may displace adjacent teeth, particularly when unerupted, but generally do not produce root resorption. They may displace the neurovascular bundle. Antero-posterior dimensions in this series ranged from 28 to 77 mm, with a mean of 50 mm.

Adolescent↗
PubMed1978

Age-standardized incidence rates of ameloblastoma and dentigerous cyst on the Witwatersrand, South Africa.

Although a great deal is known about the incidence of cancer, including oral cancer, no such study has been done on odontogenic tumors and jaw cysts. There are therefore no standardized data which would allow for comparative incidences in different countries and between different groups. In the present study, cases of ameloblastomas and dentigerous cysts derived from the records of all the hospital pathology departments and private pathology practices on the Witwatersrand, were recorded for the 10-year period 1965--1974. The population at risk (1970 census) was 974,390 Whites and 1,567,280 Blacks. The annual incidence rates, standardized against the standard world population, for ameloblastomas per million population are 1.96, 1.20, 0.18 and 0.44 for Black males, females and White males, females, respectively. The equivalent four figures for dentigerous cysts are 1.18, 1.22, 9.92 and 7.26. These figures show that ameloblastoma is very much more common in Blacks than Whites in the population at risk. Conversely, dentigerous cysts are much more common in Whites. This makes it unlikely that dentigerous cysts predispose to ameloblastoma formation. These epidemiologic observations give rise to speculation as to whether some component of the South African Black diet or other environmental substance might possibly be an etiologic factor in ameloblastoma.

Ameloblastoma↗