Advanced methods in the evaluation of premalignant lesions and carcinomas of the oral mucosa

Potency of Pfeiffer's Crystallization to Analyze Oral Leukoplakia and Squamous Cell Carcinoma

OBJECTIVE

Oral cancer usually has an early precancerous stage before its actual malignant transformation. Although there are various approaches to diagnose early stages of cancer, yet there is one less explored, cost effective and simple technique known as crystallization test. The aim of the study was to reaffirm the effectiveness of Pfeiffer's crystallization test in screening oral leukoplakia and squamous cell carcinoma.

METHODS

Fifty oral leukoplakia, sixty five oral squamous cell carcinoma and sixty healthy individuals participated in crystallization test. Single blood drop was used to perform the test and obtained crystal patterns were analysed. Cross tabulation and Chi-Square test was performed to find the frequency and association between the groups. Kruskal-Wallis H test and Mann Whitney U test was applied comparing mean transverse form.

RESULTS

Sensitivity of crystallization test was 80% and 93.84% in oral leukoplakia and squamous cell carcinoma. Chi-Square analysis revealed highly significant transverse form between the study groups (p < 0.000).

CONCLUSION

Crystallization test proves to be simple, reliable and minimal invasive diagnostic approach under strictly maintained physical conditions.

Morphological Analysis of Elastic Fibers in Various Grades of Oral Squamous Cell Carcinoma and Epithelial Dysplasia Using Verhoeff-Van Gieson Stain

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the sixth most common malignancy in India. The aggressiveness of OSCC is analyzed not only based on the dysplastic features and tumor infiltration pattern, but also by means of the stromal changes that pave the way for an invasion into the connective tissue. The role of elastic fibers in the progression of OSCC is still unknown because of sparse literature and the masking effect of overlying inflammatory cells and the lower number of elastic fibers in the lamina propria. The present study provides further insight into the qualitative assessment of elastic fibers in various grades of dysplasia and OSCC.

OBJECTIVES

To analyze the morphological changes exhibited by the elastic fibers in epithelial dysplasia and OSCC.

MATERIALS AND METHODS

Two sections were cut from each of 60 samples of varying grades of OSCC and 60 samples of varying grades of epithelial dysplasia followed by staining with hematoxylin and eosin and Verhoeff-Van Gieson stain.

RESULTS

Statistically significant results were obtained for qualitative analysis of elastic fibers. A change in density and orientation to overlying epithelium and tumor islands was seen on progressing from well-differentiated to poorly differentiated OSCC and in progressing grades of dysplasia.

CONCLUSION

The uniqueness of this study lies in the exploration of elastic fibers in dysplasia and well-differentiated OSCC, a less explored field. The study of the connective tissue stromal changes can be used as an adjunct to histological grading.

Assessment of DNA Damage in Leukoplakia Patients with Different Degrees of Dysplasia

BACKGROUND

Single cell gel electrophoresis (SCGE) assay also known as comet assay is a rapid and highly sensitive fluorescent molecular technique for detecting various forms of deoxyribonucleic acid (DNA) damage at individual cellular level.

MATERIALS AND METHODS

The present study was done to detect the extent of DNA damage in oral leukoplakia (OL) and compare with normal individuals. The sample population was obtained from an outpatient clinic of a tertiary teaching dental institute. A total of 36 consecutive patients with leukoplakia and 10 healthy normal volunteers were recruited for the study and assessed for the extent of DNA damage using SCGE following clinical diagnosis and histological grading. Peripheral blood was obtained by venipuncture and SCGE assay was performed. Mean comet tail length was recorded and analyzed statistically to compare the extent of damage in each group.

RESULTS

The mean comet tail length seen in leukoplakia patients with moderate to severe dysplasia was 1.25 ± 0.14 mm while for the control subjects, it was 0.31 ± 0.10 mm. The difference was statistically significant (p = 0.000). On comparing within the grades of leukoplakia, a progressive trend of increasing tail length was observed with increasing grades of dysplasia.

CONCLUSION

Deoxyribonucleic acid damage as measured by SCGE is seen in leukoplakia. A stepwise increase in DNA damage levels from healthy controls, through patients with non-dysplastic epithelium to varying grades of dysplasia has been observed indicating the extent of DNA damage in this high risk group.

Role of serum ß-carotene in the diagnosis and prevention of oral squamous cell carcinoma - a case control study

CONTEXT

Oral squamous cell carcinoma (OSCC) is the most common cancer of the head and neck. It accounts for more than 90% of all malignancies Which occur in the head and neck region. The high incidence and mortality rate of oral cancer stimulates continuation of research on finding new diagnostic tools or markers for it.

AIM

To evaluate the possible role of serum β-carotene as a biochemical parameter in the diagnosis of oral squamous cell carcinoma.

MATERIALS AND METHODS

The serumβ-carotene levels in 40 patients with clinically diagnosed and histopathologically confirmed oral squamous cell carcinoma were estimated and the levels were compared with those of 40 healthy controls. The serum β-carotene levels were estimated by using a spectrophotometer. The data which was obtained was analyzed statistically by using unpaired t-test.

RESULTS

Subjects with oral squamous cell carcinoma showed significantly lower levels of mean serum β-carotene (149.95 ± 61.29) as compared to those seen in controls (278.19 ± 90.12).

CONCLUSION

The results of the present study are encouraging and they suggest that the estimation of the low levels of β-carotene in the patients with oral squamous cell carcinoma may be a useful diagnostic tool for making the diagnosis of oral squamous Cell carcinoma and thereby improving the prognosis of this dreaded disease.

Automated Diagnosis of Oral Cancer Using Higher Order Spectra Features and Local Binary Pattern: A Comparative Study

In the field of quantitative microscopy, textural information plays a significant role very often in tissue characterization and diagnosis, in addition to morphology and intensity. The objective of this work is to improve the classification accuracy based on textural features for the development of a computer assisted screening of oral sub-mucous fibrosis (OSF). In fact, the approach introduced is used to grade the histopathological tissue sections into normal, OSF without dysplasia (OSFWD) and OSF with dysplasia (OSFD), which would help the oral onco-pathologists to screen the subjects rapidly. The main objective of this work is to evaluate the use of Higher Order Spectra (HOS) features and Local Binary Pattern (LBP) features extracted from the epithelial layer in classifying normal, OSFWD and OSFD. For this purpose, we extracted twenty three HOS features and nine LBP features and fed them to a Support Vector Machine (SVM) for automated diagnosis. One hundred and fifty eight images (90 normal, 42 OSFWD and 26 OSFD images) were used for analysis. LBP features provide a good sensitivity of 82.85% and specificity of 87.84%, and the HOS features provide higher values of sensitivity (94.07%) and specificity (93.33%) using SVM classifier. The proposed system, can be used as an adjunct tool by the onco-pathologists to cross-check their diagnosis.

PCNA and p53 expression in oral leukoplakia with different degrees of keratinization

Leukoplakias are oral lesions that may have many clinical and histological aspects and they are usually associated with malignancy when dysplastic alterations are shown. However, these transformations may occur in non-dysplastic lesions that show harmless clinical aspect. For this reason, the proposal was to study the p53 and PCNA immunohistochemical expression in non-dysplastic leukoplakias, trying to correlate the results only with the epithelial keratinization degree. For this, 24 leukoplakias degrees I, II and III of Grinspan were used, all of them located in oral mucosa. Most of the leukoplakias showed p53 and PCNA expression in their different keratinization degrees. The p53 marking was confined to the basal and parabasal layers, while the PCNA marking occurred in practically all epithelial layers. The expression pattern of these markers was histologically and statistically similar between the lesions with these keratinization variations. It was evident that non-dysplastic epithelium of leukoplakias showed submicroscopical signs of alterations that lead to malignant transformation, and that the keratinization degree did not correlate to a greater risk of this event.

Carcinogenicity and Chronic Toxicity in Mice and Rats Administered Vinyl Acetate Monomer in Drinking Water

Carcinogenicity and chronic toxicity of vinyl acetate monomer (VA) were examined in male and female Crj:BDF1 mice and F344/DuCrj Rats. Groups of 50 mice and 50 rats of each sex were orally administered VA in drinking water containing 0, 400, 2,000 or 10,000 ppm (g/g) VA for 104 wk. Squamous cell tumors were clearly evident in the upper digestive tract of treated mice and rats, and in the larynx of treated mice of both sexes. In mice, squamous cell carcinomas and papillomas were observed in the oral cavity, esophagus, forestomach and larynx of the 10,000 ppm group, together with basal cell hyperplasia, squamous cell hyperplasia and epithelial dysplasia. In rats, incidences of squamous cell carcinomas and papillomas were increased in the oral cavity of the 10,000 ppm group of both sexes, and an esophagus squamous cell carcinoma was observed in a 10,000 ppm female. Pre-neoplastic hyperplasias were also noted. Mapping of the neoplastic and pre-neoplastic lesions in the oral cavity of the 10,000 ppm group revealed that both the lesions occurred predominantly at Level V in mice and at Level VI in rats. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of mice and rats and the estimated daily VA intakes per body weight, and compared with literature values.

Immunohistochemical study of syndecan-1 down-regulation and the expression of p53 protein or Ki-67 antigen in oral leukoplakia with or without epithelial dysplasia

BACKGROUND

Leukoplakia is an oral pre-cancerous lesion that sometimes develops into squamous cell carcinoma. Therefore, leukoplakia with epithelial dysplasia is useful for studying carcinogenesis at the cellular level. The purpose of this study was to evaluate a potential association between the loss of syndecan-1 expression and the expression of p53 protein and Ki-67 antigen, and to identify reliable markers for predicting malignant changes in oral leukoplakia with epithelial dysplasia.

METHODS

Changes in the expression of syndecan-1, p53, and Ki-67 were examined immunohistochemically in 43 cases of oral leukoplakia with or without epithelial dysplasia. The subjects were categorized as: none, 13 cases; mild dysplasia, 5 cases; moderate dysplasia, 17 cases; and severe dysplasia, 8 cases. The expression of these molecules in normal oral epithelia (22 cases) was also investigated.

RESULTS

Strong syndecan-1 expression was observed on the surface of keratinocytes in normal epithelium. Immunopositivity was lost gradually as the extent of epithelial dysplasia increased. In normal epithelium, p53 and Ki-67 appeared mainly in the basal cell layer, while they were more widely distributed in leukoplakia. Specifically, significant changes were observed in the labeling index of p53 and Ki-67 in leukoplakia as epithelial dysplasia progressed from mild to moderate or severe.

CONCLUSION

Our results reveal that overexpression of p53 protein and Ki-67 antigen, and down-regulation of syndecan-1 expression in the lower part of the epithelium, are associated with dysplastic changes. Therefore, the down-regulation of syndecan-1 expression may be the most important reliable marker for dysplastic changes.

Histopathological and immunohistochemical study of malignant transformation of oral leukoplakia, with special reference to apoptosis-related gene products and proliferative activity

OBJECTIVE

To examine the frequency of apoptosis in oral leukoplakia and its relationship with pathological parameters, including Ki-67 expression, and with the expression of p53, Bcl-2 and Bax proteins. MATERIAL AND MEHODS: Clinical, histopathological and immunohistochemical studies were carried out and the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling method was used to verify the apoptosis and its mechanism of genetic control of the development, progression and promotion of lesions. The material consisted of five normal mucosal epithelia. six leukoplakias without malignant transformation and seven leukoplakias with malignant transformation. Based on counts of 10 fields at a magnification of x 400, mitotic, apoptotic and Ki-67 indices were calculated, and p53, Bcl-2 and Bax expressions were recorded.

RESULTS

The peak of the mitotic and Ki-67 indices and p53 expression shifted basally, possibly as a result of malignant transformation, whilst the peak of apoptosis and the expression of apoptotic-related proteins in oral leukoplakia showed no transformation.

CONCLUSION

The frequent expression of Bcl-2 in oral leukoplakia with malignant transformation combined with the reduction in the number of apoptotic cells indicated that malignancy occurred as a result of the avoidance of apoptosis. In addition, high levels of Bax expression in oral leukoplakia without malignant transformation indicated that the Bcl family may play a role in the progression of the disease.

Suprabasal p53 immunoexpression is strongly associated with high grade dysplasia and risk for malignant transformation in potentially malignant oral lesions from Northern Ireland

AIMS

No good predictive marker for the malignant transformation of potentially malignant oral lesions (PMOLs) is currently available. This study re-evaluated the value of p53 immunoexpression to predict malignant transformation of PMOLs after discounting possible confounding factors.

METHODS

PMOLs from 18 patients who showed progression to carcinoma, 16 of the respective carcinomas, and PMOLs from 18 matched controls were evaluated by immunohistochemistry (IHC) for p53 expression. A mouse monoclonal antibody that detects wild-type and mutant forms of human p53 was used. The p53 immunostaining pattern was also correlated with the degree of dysplasia.

RESULTS

Suprabasal p53 staining was significantly associated with high grades of dysplasia (p < 0.01). The specificity and positive predictive value (PPV) for malignant transformation of suprabasal p53 staining were superior to the assessment of dysplasia, but sensitivity was inferior. All carcinomas derived from PMOLs with suprabasal p53 showed strong p53 immunostaining. However, the absence of suprabasal p53 staining and/or dysplastic changes did not preclude malignant transformation in a considerable proportion of PMOLs.

CONCLUSIONS

This study confirms and extends previous findings that suprabasal p53 immunoexpression has a high PPV for malignant transformation of PMOLs and can be used as a specific marker for lesions that are at high risk for malignant transformation. The absence of suprabasal p53 staining (that is, absence of, or basal, p53 staining) is non-informative for prognostic purposes. Because of its limited sensitivity, p53 IHC is not a substitute for the assessment of dysplasia in the evaluation of PMOLs. Instead, p53 IHC emerges as a clinically useful supplement of histopathological assessment in the prognosis of PMOLs.

Does type II nitric oxide synthase expression correlate with cellular proliferation in oral squamous cell carcinoma and dysplasia?

BACKGROUND

Nitric oxide (NO) has been implicated both in tumor progression and inhibition. This study investigated whether type II nitric oxide synthase (NOS2) expression correlated with cell proliferation in oral squamous cell carcinoma (OSCC) and dysplasia.

METHODS

Paraffin-embedded tissue samples of normal oral mucosa, OSCC, and dysplasia were assessed immunohistochemically using monoclonal antibodies to NOS2 and Ki-67 antigen. We used Western blotting to confirm NOS2 antibody specificity and protein expression in select cases.

RESULTS

NOS2 staining was increased in OSCC relative to normal oral mucosa, in which no expression was found. Both NOS2 expression and Ki-67 indices independently correlated with grade of dysplasia (p < .001) but not with the degree of tumor differentiation. A positive correlation was found between NOS2 expression and Ki-67 in cases of mild and moderate dysplasia (p < .001), but not in severe dysplasia and OSCC.

CONCLUSIONS

No correlation exists between Ki-67 and NOS2 expression in severe dysplasia and OSCC. The findings suggest that the level of NO produced by NOS2 is insufficient to affect cellular proliferation in these conditions. The mechanism of NOS2 activation and the consequences of its expression remain to be fully explained.

Expression of inducible nitric oxide synthase and p53 in oral epithelial dysplasia

AIM

Nitric oxide (NO) has been studied in a variety of human cancers and is implicated in both tumor promotion and inhibition. Downregulation of the enzyme iNOS by wild-type p53 (but not mutant) protein has been shown to occur in normal cells and some tumors, but the relationship has not been reported in oral epithelial dysplasia.

METHODS AND RESULTS

An immunohistochemical study was conducted with antibodies to iNOS and p53 (clone DO-7) in 36 cases of oral dysplasia of varying severity. Statistical analysis showed a significant correlation between iNOS staining and grade of dysplasia (P <.001) and between p53 and iNOS staining (P <.001).

CONCLUSIONS

This preliminary study has shown that iNOS expression correlates with severity of dysplasia, and it is also increased in those cases showing positive staining for p53. Further research is required to fully establish the relationship between iNOS and p53 in both dysplasia and oral squamous cell carcinoma.

Bcl-2 expression in sequential biopsies of potentially malignant oral mucosal lesions assessed by immunocytochemistry

OBJECTIVE

To examine, for the first time Bcl-2 expression in sequential (autogenous) oral mucosal biopsies taken from the same sites in a gender, risk-factor matched, Caucasoid sample, over a 21-year period.

DESIGN

Retrospective immunocytochemical longitudinal study of archival serial biopsies.

MATERIALS AND METHODS

Computer records were used to identify biopsy specimens derived from 12 patients. These were divided into four groups: (1) Histologically innocuous lesions which remained histologically innocuous. (2) Dysplastic lesions which remained dysplastic. (3) Histologically innocuous lesions which later progressed to squamous cell carcinoma (SCC). (4) Dysplastic lesions which later progressed to SCC. This represented 65 biopsies in total. Bcl-2 expression was studied using mouse antihuman BCL-2 oncoprotein clone 124 (Dako, Denmark).

RESULTS

Generally, there was a lack of Bcl-2 immunoreactivity in the epithelium, with one exception in dysplastic epithelium from a group (3) patient.

CONCLUSION

These findings suggest that in our series, Bcl-2 is not expressed early in oral premalignant lesions and appears to contradict previous reports. Possible explanations for this disparity are considered.

Does expression of inducible nitric oxide synthase correlate with severity of oral epithelial dysplasia?

The small molecule nitric oxide (NO) has generated an exponential amount of research since its discovery as a biological messenger in 1987. It has a vast number of actions, many of which are poorly understood. It has been studied in a variety of human cancers and has been implicated both in tumour promotion and inhibition. Although NO is produced by three distinct isoforms of the enzyme nitric oxide synthase (NOS), most cancer research is directed towards the calcium-independent form, iNOS which following induction, produces much higher quantities of NO than the other two. In this study the expression of iNOS is assessed by immunohistochemistry in 26 cases of oral epithelial dysplasia ranging in severity from mild to severe. iNOS staining was found in all 26 cases of dysplasia with the degree of staining correlating to the severity of dysplasia (p < 0.001). There was no iNOS staining seen in adjacent normal epithelium. The possible role of iNOS in the complex transformation from dysplasia to invasive oral cancer and the clinical applications are discussed.

Carbon dioxide laser evaporation of leukoplakia of the lower lip: a retrospective evaluation

The purpose of this study was the retrospective evaluation of the treatment results of CO2 laser evaporation for 27 cases of leukoplakia of the lip. The data were derived from 23 patients who presented with leukoplakia of the lower lip during the period 1978-96. Four patients developed a second primary leukoplakia of the lip resulting in 27 cases of leukoplakia. All lesions were treated with a CO2 laser equipped with an operation microscope and micromanipulator. Short-term evaluation showed complete epithelialisation 4 weeks after CO2 laser evaporation; there was minimal scar formation and no subsequent interference with normal lip function. During long-term evaluation, four recurrences (14.8%) were diagnosed which developed between 5 and 31 months after treatment, these were retreated with CO2 laser evaporation. There was no development of squamous cell carcinoma in the CO2 laser-treated area. Selective removal of affected epithelium with minimal damage to surrounding structures is possible using CO2 laser evaporation, followed by excellent wound healing and good functional result. Treatment can be performed under local anaesthesia on an outpatient basis. The recurrence rate is low compared with the recurrence rate after surgical excision. Therefore, CO2 laser evaporation is considered a reliable and effective treatment modality for leukoplakia of the lip.

Oral cancer: role of the basement membrane in invasion

Invasive growth of cancer cells is a complex process involving specific interactions between tumour cells and the orderly, integrated complexes of the extracellular matrix. Basement membranes have been proposed as one constituent of extracellular matrix which carries responsibility for regulating invasion and metastasis. Using a chemically induced rat tongue carcinoma model, it has been shown that components of the basement membrane and its overall structure are altered during tumour invasion, and methods have been developed to quantitate some of these differences. Since the basement membrane can be specifically characterized by its fibrous protein network of Type IV collagen and laminin, which is embedded in a heparan sulphate-rich proteoglycan matrix, these components have been targeted. In particular, the current paper presents results in the context of current concepts of early changes in neoplastic invasion of underlying connective tissues. In consequence, further elaboration of the underlying mechanisms of epithelial migration in oral cancer may allow an exploration of the use of alterations in expression of basement membrane components as prognostic indicators.

A comparison of the management of potentially malignant oral mucosal lesions by oral medicine practitioners and oral & maxillofacial surgeons in the UK

This study describes the results of a survey undertaken to assess the management of potentially malignant oral mucosal lesions by oral medicine practitioners and compares their approach with that of oral & maxillofacial surgeons that we have previously described. Significant differences were noted between the two groups in the use of photography to document the lesions and in the use of certain special investigations, which included measurement of serum iron, serum ferritin, serum Vit B12, red cell folate and candidal isolation. The groups also varied in the perceived importance of the age of the patient and anatomical site of the lesion when deciding on the need for further biopsy. There was also significant variation in the use of certain treatment modalities, including excising non-dysplastic and severely dysplastic/carcinoma in-situ lesions and eliminating trauma when treating mild/moderately dysplastic and severely dysplastic/carcinoma in-situ lesions. Significant differences in the frequency and duration of follow-up were noted for non-dysplastic lesions. Finally, the two groups differed significantly when asked to rank the perceived importance of certain factors (the histopathology of the most recent biopsy and the anatomical site of the lesion) when deciding the need to follow-up. Possible reasons for the variation are discussed.

Proliferative activity and loss of function of tumour suppressor genes as 'biomarkers' in diagnosis and prognosis of benign and preneoplastic oral lesions and oral squamous cell carcinoma

Oral cancer is a disease of the elderly and is closely connected with cigarette smoking and alcohol consumption. Since the successful introduction of multidisciplinary treatment, the survival rate has not changed. Because of the high mortality and potentially disfiguring treatment, today's efforts are aimed at eliminating risk factors, chemoprophylaxis, improvement in diagnostic procedures, and understanding of the genetic mechanisms of oral carcinogenesis. Immunohistochemical and molecular biology analysis of biopsy tissue and cell lines of preneoplastic and neoplastic lesions that originate from the oral mucosa have shown that alterations in tumour suppressor genes such as p53 and Rb gene may have an important role in oral carcinogenesis and may be potentially useful prognostic 'biomarkers' in oral carcinogenesis. Statistical analysis of immunohistochemical data from 216 patients did not identify significant or consistent differences of p53, MDM2, or RB expression with respect to stage of disease, malignant transformation, metastatic node involvement, recurrence, or survival. Nevertheless, p53 overexpression seems to correlate strongly with histological progression of the disease, which confirms the importance of p53 alterations in oral carcinogenesis. Overexpression of p53 is usually found in the less differentiated proliferating cells in benign and malignant oral lesions. Assessment of the proliferating activity is possible by immunohistochemical staining with monoclonal antibodies against proliferating nuclear antigen and Ki-67. Statistical analysis shows that overexpression of p53 combined with high proliferative activity predicts a less favourable course of disease in oral squamous cell carcinoma.

Flow cytometric analysis of cell cycle fractions in oral leukoplakia

Flow cytometric analysis of cell cycle fractions and DNA ploidy was performed on 39 biopsy specimens of oral leukoplakia. The aneuploidy rate of these leukoplakias was 9/39 (23.1%) and the mean DNA index of the aneuploid lesions was 1.34. The aneuploidy rate was significantly higher in severely dysplastic lesions (8/17) than in mildly dysplastic (1/15, P<0.02) and nondysplastic (0/7, P<0.05) lesions. No significant differences in the percentages of each cell cycle fraction were seen between the diploid and the aneuploid leukoplakias. However, the S-phase fraction of the severely dysplastic lesions (23.0%) among the diploid leukoplakias was higher than those of the mildly dysplastic (12.4%) and nondysplastic (15.5%) lesions, and the difference between the severely dysplastic and the mildly dysplastic lesions was statistically significant (P<0.001). These results suggest that flow cytometric analysis of cell cycle fractions and DNA ploidy might offer additional information for assessing the malignant potential of oral leukoplakias.

Oral leukoplakia: a clinicopathological review

Leukoplakia is the most common premalignant or potentially malignant lesion of the oral mucosa. It seems preferable to use the term leukoplakia as a clinical term only. When a biopsy is taken, the term leukoplakia should be replaced by the diagnosis obtained histologically. The annual percentage of malignant transformation varies in different parts of the world, probably as a result of differences in tobacco and dietary habits. Although epithelial dysplasia is an important predictive factor of malignant transformation, it should be realized that not all dysplastic lesions will become malignant. On the other hand non-dysplastic lesions may become malignant as well. In some parts of the world the tongue and the floor of the mouth can be considered to be high-risk sites with regard to malignant transformation of leukoplakia, while this does not have to be the case in other parts of the world. The cessation of tobacco habits, being the most common known aetiological factor of oral leukoplakia, has been shown to be an effective measure with regard to the incidence of leukoplakia and, thereby, the incidence of oral cancer as well. Screening for oral precancer may be indicated in individuals at risk.

Morphological assessment of malignant potential of epithelial hyperplastic lesions

The spectrum of conventional and advanced morphological methods for the assessment of malignant potential of precancerous lesions of the laryngeal mucosa is discussed.

Immunohistochemical staining of desmosomal components in oral squamous cell carcinomas and its association with tumour behaviour

Desmosomes are intercellular junctions that have been shown to be down-regulated in certain types of carcinomas and that may play a role in suppression of invasion and metastasis. We have shown previously that immunohistochemical staining for the major desmosomal glycoprotein, desmoglein (Dsg), is reduced in some cases of squamous cell carcinoma (SCC) of the head and neck, and that reduced staining correlates with lymph node involvement. Desmosomes are multicomponent organelles. We therefore sought to determine whether another major desmosomal molecule, desmoplakin (Dp), showed similar reduced expression to that shown by desmoglein. We have stained 65 specimens of primary SCC of the oral cavity (37 non-metastatic and 28 metatastic) with monoclonal antibodies to both desmoglein and desmoplakin. We show that reduction of Dp staining correlates with loss of differentiation of the primary tumour, degree of invasion and presence of lymph node metastases. Similar correlations were found with Dsg staining. There was also correlation between reduction in Dp staining and reduction in Dsg staining. It is concluded that down-regulation of desmosomal expression occurs in some cases of SCC of the oral cavity and is associated with invasion and metastasis. Desmosomes may have an invasion and metastasis suppressor function.

Mode of tumor invasion in oral squamous cell carcinoma: improved grading based on immunohistochemical examination of extracellular matrices

BACKGROUND

To predict the nodal involvement of oral squamous cell carcinoma (OSCC) many investigators have studied the histologic features of primary tumors. However, conventional histologic grading still is not sufficient to provide an objective and practical evaluation. In this study we tried to modify one standard type of histologic grading, namely, mode of invasion (MI), on the basis of the extracellular matrix (ECM) staining pattern.

METHODS

One hundred seventeen initial biopsies of primary OSCC were histologically examined, and the MI was graded. The expression of a series of ECMs-laminin, type IV collagen, heparin-sulphate proteoglycan, fibronectin, tenascin, decorin, and vitronectin-was immunohistochemically examined.

RESULTS

The ECM staining pattern showed a close association with the MI, and was classified into types I and II. The type I staining pattern was observed in the noninvasive cases (MI grades 1 and 2), while type II was in the highly invasive cases (MI grades 4c and 4d). Because the ECM staining pattern in the moderately invasive cases (MI grade 3) included both types I and II, these cases were subdivided and compared. As a result, the type II cases showed a significantly higher incidence of nodal involvement than did the type I cases.

CONCLUSION

An examination of a series of the ECMs, in addition to the conventional histologic examination, is thus considered to provide more objective and practical data to evaluate the invasive and metastatic potential of OSCC.

Management of potentially malignant oral mucosal lesions by consultant UK oral and maxillofacial surgeons

This paper describes the results of a recent survey carried out under the auspices of the Professional Education and Evaluation Subgroup of the UK Working Group on Screening for Oral Cancer and Precancer. The aim of this survey was to assimilate information regarding currently used management options of potentially malignant oral lesions as a basis from which to rationalise our future approach to their management. The survey has confirmed that variation exists among oral and maxillofacial consultants in their approaches and a more formal approach to management may therefore be indicated.

A proposal for a classification and staging system for oral leukoplakia: a preliminary study

A classification and staging system for oral leukoplakia is proposed based on the recently revised definition of this premalignant lesion. The initial experiences of this system are described on the basis of 100 patients with oral leukoplakia. The new classification and staging system seems very suitable for characterizing groups of patients with oral leukoplakia. Whether this system is also valuable with regard to guidelines for management of these patients has still to be proven.

Flow cytometric analysis of nuclear DNA content in oral leukoplakia: relation to clinicopathologic findings

DNA ploidy of 50 biopsy specimens of oral leukoplakia was investigated by flow cytometry, and the results were compared with the clinicopathologic appearances. The aneuploidy rate of the leukoplakias was 17/50 (34%), and the mean DNA index (DI) of the aneuploid lesions was 1.22, with a range from 0.70 to 1.84. The incidence of the aneuploidy was significantly (P < 0.01) higher in nonhomogeneous leukoplakias (11/18) than in homogeneous lesions (6/32). The aneuploidy rate of the severely dysplastic leukoplakias (11/17) was significantly higher than those of the mildly dysplastic (4/22; P < 0.01) and the nondysplastic (2/11; P < 0.02) lesions. A significant (P < 0.01) difference in the aneuploidy rate was also observed between tongue (12/23) and gingival (2/18) leukoplakias.

p53 expression in the carcinogenesis in the oral mucosa

Hyperplastic lesions of the oral mucosa such as leukoplakia and oral lichen planus can eventually develop into squamous cell carcinomas. In the clinical treatment of these lesions it would be very important to be able to predict the biological behaviour of an individual lesion. In 64 hyperplastic lesions and 85 squamous cell carcinomas of the oral mucosa, the expression of the mutant tumor suppressor gene p53 was investigated. A positive correlation was seen between the expression of the mutant tumor suppressor gene p53 and the grade of dysplasia of the lesions.

Scanning electron microscopy of different types of oral leukoplakia: comparison with normal and malignant oral mucosa

The present study analysed surface architecture of normal, premalignant and malignant oral mucosa using scanning electron microscopy to evaluate its role in early diagnosis of potentially malignant oral lesions. The surface ultrastructure of the buccal mucosa in tobacco chewers showed variations from that of non-chewers. Homogenous leukoplakia demonstrated well-defined intercellular junctions and the microrugal surface pattern as seen in normal mucosa. In verrucous leukoplakia, the surface layer consisted of characteristically-shrunken desquamated hyperkeratotic cells. Erosive leukoplakia had a discontinuous superficial layer along with complete loss of intercellular ridges. Speckled leukoplakia also showed marked abnormalities such as thickened irregular protrusions and evidence of a villus-like pattern. These villus-like structures were comparatively prominent in leukoplakia showing dysplasia. Oral carcinoma showed marked altered surface ultrastructure and had a pattern similar to dysplastic lesions. The irregular swollen elongated protrusions with villous-like structures that were observed in carcinoma and dysplastic lesions can, therefore, be considered as surface markers for potentially malignant leukoplakia.

p53 and PCNA expression in carcinogenesis of the oropharyngeal mucosa

Hyperplastic lesions of the oral mucosa such as leukoplakia and oral lichen planus can eventually develop into squamous cell carcinomas (SCC) and provide an excellent model for multistage carcinogenesis. The development of carcinomas is assumed to be the result of interaction of genetic factors, locally applied carcinogens and immunological unresponsiveness. The purpose of this study was, therefore, to determine the role of alterations of the tumour suppressor gene p53, and the proliferation status of the lesions determined by PCNA expression. We investigated p53 and PCNA expression in 265 tissue sections of normal mucosa, premalignant, malignant and metastatic lesions of the oral mucosa by immunohistology. Quantitative analysis showed a gradual increase in PCNA expression from normal mucosa to moderately differentiated SCC. p53 expression was detectable in benign premalignant lesions. The increase in the number of p53-positive biopsies was correlated with the dysplasia and loss of differentiation in the premalignant and malignant lesions.

Expression of human cytokeratin 14 in normal, premalignant and malignant oral tissue following isolation by plaque differential hybridisation

Differences in gene transcription between RNA samples extracted from oral normal and squamous cell carcinoma (SCC) tissue were examined using the technique of cDNA library differential plaque screening. A differentially expressed transcript was selected on the basis of it being under-expressed in the cancer tissue and was identified, using DNA sequencing, as cytokeratin 14. The level of cytokeratin 14 transcription in RNA samples extracted from a range of oral SCC and normal tissue, as well as "white patch" lesions, was then investigated. Cytokeratin 14 appeared to be significantly under-expressed in oral cancer specimens studied compared to normal and white-patch tissue (P < 0.01). The trend for higher levels of cytokeratin 14 transcription in the dysplastic "white patch" samples compared to that observed for the malignant tissue (P < 0.05) suggests that the decrease in cytokeratin 14 transcription is a late event in the carcinogenic pathway.

Tissue markers of potentially malignant human oral epithelial lesions

Tissue markers of potential malignancy have been sought for many years. Cell surface markers, particularly blood group and histocompatibility antigens, have shown great promise and several squamous carcinoma antigens have been identified--but not fully studied in potentially malignant lesions. Growth factors and receptors also need further study. Cytoplasmic markers of potential malignancy have been examined and, of these, keratins, filaggrin, and some carcinoma antigens show most promise. Nuclear analyses have promise but are time-consuming and expensive. Image cytometric analyses appear to be sensitive and predictive: oncogene and tumour suppressor analyses remain to be fully evaluated. New investigative techniques at the cellular and molecular level show increasing promise at defining potentially malignant oral epithelial lesions but more prospective studies are required.

Nucleolar organiser region (NOR) distribution as a diagnostic marker in oral keratosis, dysplasia and squamous cell carcinoma

Nucleolar organiser regions (NORs) were quantified from a range of oral mucosal biopsies (n = 40) consisting of benign, reactive, dysplastic and carcinomatous lesions, using silver (Ag) staining, to see if AgNOR counts were helpful in distinguishing them. Mean counts were greater in carcinomas (8.37 +/- 6.11) compared to epithelial dysplasias (5.61 +/- 4.63) or benign keratoses (4.51 +/- 2.57). Although these differences were significant, counts in each diagnostic group overlapped so much that they were of no practical value in distinguishing between individual lesions. However, the higher counts found in many carcinomas were due to dispersion of AgNORs within the nucleoplasm, so that the AgNOR type is helpful in making such a distinction. Whether those dysplastic lesions with higher and more dispersed counts represent those at greater risk of malignant transformation awaits longitudinal study.

Immunohistochemical detection of desmosomes in oral squamous cell carcinomas: correlation with differentiation, mode of invasion, and metastatic potential

An expression of desmosomal glycoprotein 1 (DG 1) was immunohistochemically examined in 77 biopsies and 21 metastatic cervical lymph nodes of oral squamous cell carcinomas (SCC). In the primary tumors the DG 1 expression was significantly reduced at the invasive site of poorly differentiated and highly invasive tumors. In cases of metastases in cervical lymph nodes, the DG 1 staining at the invasive site of the primary tumor was significantly less than that of nonmetastatic cases. The DG 1 expression in the metastatic lymph nodes was as weak as that in the primary tumor. Thus, we suggest that immunohistochemical investigation of DG 1 expression in oral SCC is valuable in predicting tumor behavior.

Expression of p53 mutant nuclear phosphoprotein in oral carcinoma and potentially malignant oral lesions

An immunohistochemical study of primary oral squamous cell carcinomas (n = 37) with a monoclonal antibody (PAb 1801) specific to p53 antioncogene product demonstrated nuclear overexpression of the mutant protein in 35% of cases. Those positive included carcinomas without deep invasion suggesting that p53 mutation may occur in the early stages of progression of a malignancy. This is supported by the observation that mutant protein was detectable in limited amounts in 2 cases of oral mucosal dysplasia (n = 12). None of the normal or reactive oral mucosal tissues (n = 17) were positive for p53. The presence or absence of p53 was not correlated with the site of the lesion or its degree of differentiation. Our data suggest that p53 gene mutations are commonly involved in oral cancer but are neither sufficient nor necessary for the development of malignancy. Nevertheless, as this mutation is the commonest genetic change described so far in cancers in white caucasoids, it is possible that its presence can be used as a marker of risk in a high proportion of malignant and potentially malignant oral lesions.

DNA analysis of oral leukoplakia by flow cytometry

DNA ploidy of 19 oral leukoplakias with and without epithelial dysplasia was investigated and the results were compared with 11 normal gingival biopsies, 14 oral benign tumours and 50 oral squamous cell carcinomas. The results suggest a possible relationship between DNA aneuploidy and oral leukoplakias or squamous cell carcinomas, as 32% of the oral leukoplakias and 48% of the oral squamous cell carcinomas were aneuploid although all the normal gingival biopsies and the benign oral tumours examined were diploid. No significant relationship was observed, however, between DNA ploidy and epithelial dysplasia in the leukoplakias.

Oncogene expression and oral cancer

Cancer of the oral cavity remains a major problem in the United States as well as in many other countries, some of which record as much as 30% of all their cancers to be in the oral region. Despite numerous advances in the fields of epidemiology and etiology, little is known of the molecular basis of oral cancer. Advances in the field of oncogenes have produced a tool to study the different stages of carcinogenesis, including transition from premalignant to malignant stages. These strategies have direct relevance to oral cancer where the premalignant stage is well defined. Preliminary studies into the expression and function of oncogenes suggest abnormalities including individual and multiple amplification of three or more types of these genes. This review briefly describes the concept of oncogenes, and their possible role in the development of neoplasia and specifically on studies in oral cancer.

Ultrastructural examination of experimentally induced premalignant lesions

Lesions induced in hamster cheek pouch using dimethylbenz(alpha)anthracene were studied by transmission electron microscopy and compared with normal tissue. Features regarded as suggestive of progression towards malignancy were: increased numbers of membrane-bound vesicles in basal cells, gaps in the lamina densa associated with widening of the lamina lucida and an irregular epithelial-connective tissue junction, the presence of cerebriform cells and frequent close association of 2 or more intra-epithelial cells (lymphocytes, cerebriform cells, Langerhans cells).

Expression of mucin type carbohydrates may supplement histologic diagnosis in oral premalignant lesions

Recent studies have shown that changes within membrane bound carbohydrates may be essential for cellular differentiation and malignant transformation. We have therefore, by means of immunohistochemistry, studied the expression of T/Tn related (Thomsen-Friedenrich) carbohydrates in 13 oral lesions with squamous cell dysplasia. The epithelial grade of dysplasia was graded as mild, moderate or severe. The following carbohydrate structures were studied: Tn, T, mucintype 3 chain H, and the sialylated derivates, sialosyl-Tn and sialosyl-T. In general, short structures were detected on the basal cells and longer structures on the more mature spinous cells. In many cases, this sequential expression was more disturbed with increasing grade of epithelial dysplasia. However, our results also showed that some lesions with the same grade of epithelial dysplasia showed different carbohydrate expression. These findings indicate that expression of carbohydrates may supplement histologic diagnosis in the evaluation of the prognosis of premalignant lesions.

Oral leukoplakia, with emphasis on malignant transformation. A follow-up study of 46 patients

A review of oral leukoplakia, based on data from the literature and experience with 84 patients is presented. The leukoplakic lesions of 3 patients developed malignant transformation within an average period of 5 years. All three patients were elderly women with idiopathic leukoplakia, in two cases of the homogeneous and in one case of the non-homogeneous type. The initial biopsy of the former two patients showed only hyperorthokeratosis without epithelial dysplasia. In the first biopsy of the third patient epithelial dysplasia was recorded. One of the patients finally died of widespread metastases. The other two have been treated surgically and are still alive.

DNA-ploidy studies in a keratocyst undergoing subsequent malignant transformation

Using techniques that allow flow cytometry to be performed on tissue stored in paraffin wax, we have examined the DNA content of cells from an odontogenic keratocyst which underwent malignant transformation. On histological examination, the primary lesion was an odontogenic keratocyst showing dysplastic changes within the squamous epithelium. Flow cytometry revealed a prominent, abnormal DNA stemline, which was also present in the subsequent squamous cell carcinoma.