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.

Morphometric analysis of suprabasal cells in oral white lesions.

Surgical specimens from the cheek mucosa of 73 patients with white lesions were studied to determine various morphometric parameters that would help differentiate between the various types of oral mucosal white lesions that carry a risk of malignant change. Four cell types were represented: traumatic keratosis, leucoplakia, candidal leucoplakia and lichen planus, in addition to a control group of normal mucosa. The shape and size of the epithelial cells in two cell compartments, parabasal and spinous, were investigated by an interactive image analysis system (IBAS-1). The results showed an increase in the cell size in the parabasal cell compartment of all the white lesions compared with the normal mucosa. In the spinous cell compartment there was an increase in the cell size in lichen planus and traumatic keratosis; leucoplakia and candidal leucoplakia showed a slight decrease in cell size compared with the normal mucosa. Attempts to discriminate between the four groups of white lesions showed that these parameters can provide a high level of separation between lichen planus and the three other groups, but not between leucoplakia, candidal leucoplakia, and traumatic keratosis.

Expression of blood group H antigen type 2 chain by oral carcinoma cells after radiotherapy.

The blood group H antigen type 2 was investigated immunohistochemically in sections of 44 surgical specimens from the oral mucosa. These comprised 35 squamous cell carcinomas obtained from 22 patients and 9 specimens of clinically healthy mucosa. The carcinoma specimens included 10 primary lesions and 25 recurrent lesions from patients who had undergone radiotherapy. The results showed that the specimens of normal oral mucosa stained at higher antibody titers than either group of carcinomas, and that postradiation recurrent tumors stained at higher titers than primary tumors. In 10 patients, both preradiation and postradiation carcinomas were examined; the postradiation lesions showed increased reactivity in 5 patients, no change in 3 patients, and a decrease in antigen reactivity in 2 patients. The expression of antigen H type 2 in the recurrent tumors appeared to correlate with the estimated daily tumor radiation dose; tumors with specific antigen staining took twice as long to recur after radiotherapy than tumors without similar staining. The results suggest that the expression of the blood group H antigen type 2 substance, being a differentiation antigen, is enhanced by the effect of radiation on the malignant cell.

The duality of the cell population in a calcifying epithelial odontogenic tumour (CEOT).

Ultrastructural findings in a case of CEOT are reported. It was found that the tumour cells consisted of two populations. One population was composed of polyhedral epithelial cells of the type described previously by other authors. These cells showed variation in size and abundant cytoplasm. They contained large numbers of electron-dense bundles of tonofilaments and numerous mitochondria. The other population was a cell having the ultrastructural characteristics of myoepithelial cells. These cells were arranged juxtaposed to the tumour epithelial cells and had very elongated profiles. They showed a lamina densa which was continuous with that in relation to the basal plasma membrane of the tumour epithelial cells and also a large number of hemidesmosomes. These cells also contained large numbers of fine filaments with electron-dense bodies similar to those described in smooth muscle cells. The amyloid-like material was found to consist of two types of structures which are probably related. One type showed sheets of low electron-dense filaments, the other aggregates of lamina densa fragments.

The nature of the amyloid-like material in a calcifying epithelial odontogenic tumour: an ultrastructural study.

An ultrastructural study was carried out to investigate the nature of an eosinophilic material, having the staining properties of amyloid, in a case of calcifying epithelial odontogenic tumour. At the electron-microscopical level, the eosinophilic masses consisted of two types of structure which are probably related. The first type appeared as sheets of fine filaments measuring 10-12 nm in diameter. The second type was in the form of aggregates of lamina densa fragments, probably secreted by the tumour epithelium. These fragments appeared to undergo some loss of electron density and became degraded into fine filaments, having similar thickness and electron density to those forming the filamentous masses. It is concluded from this study that the fine filamentous material is a form of amyloid which results from degradation of lamina densa material.

Expression of the CA1 determinant by carcinomas and by non-malignant epithelial cells in oral lesions.

The expression of the Ca antigen was investigated in 5 groups of oral lesions comprising 7 squamous cell carcinomas, 2 pre-invasive carcinomas, 7 lesions of types believed to predispose to carcinoma, 19 lesions of types that do not predispose to carcinoma and 5 biopsies of normal oral mucosa. Using an indirect immunoperoxidase method, the neoplastic epithelium reacted positively with the Ca1 antibody in only 4 out of 7 oral squamous cell carcinomas and the reaction varied between the specimens as to the intensity and number of positively stained cells. Several benign oral lesions specifically bound the Ca1 antibody in areas of epithelium showing infiltration with inflammatory cells. These lesions comprised 5 fibrous epulides, 1 pyogenic granuloma, 1 denture-induced hyperplasia and 1 non-diagnostic ulcer. We conclude that the Ca1 antibody is not sufficiently specific for the carcinoma to be of value in the diagnosis of malignant and premalignant lesions of the oral mucosa.

The nature of the hyaline rings in chronic periostitis and other conditions: an ultrastructural study.

The hyaline rings found in chronic periostitis and a radicular cyst were investigated ultrastructurally. These rings were composed of fine fibrillar material which was probably derived from degraded collagen fibrils, all of which eventually became degraded and unrecognizable. Foreign-body material in the form of circular bodies of probable plant origin were also found and should not be confused with the hyaline rings.

Computers in clinical and laboratory diagnosis.

Even though the process of reaching a diagnosis from the available information was first described mathematically over 200 years ago, it is only recently that computers have been applied to the problem. Examples are given to the type of approach that has been used in differentiating between possible alternative causes of conditions such as jaundice or acute abdominal pain and it is shown that the computer programme can give results at least as accurate as the most skilled clinician and usually in a much shorter time. The application of computers to problems of diagnosis in histopathology is discussed and the method of cluster analysis is illustrated in relation to the differentiation between lichen planus and leukoplakia. There appears to be some possibility of identifying patients among the group with leukoplakia who were most likely to develop a carcinoma.