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A red or blue mucous membrane disorder of the oral cavity can arise in response to a local cause of irritation, as a cause of an inflammation reaction to an infection, an auto-immune reaction to a local factor, and as an expression of an underlying systemic disorder. Moreover, it can be an expression of a premalignant or malignant mucous membrane disorder. Knowledge about and recognition of the different red and blue mucous membrane disorders can hasten the diagnosis and possible treatment. In the case of a premalignant (erythroplakia) or a malignant mucous membrane disorder (squamous cell carcinoma), the prognosis is better with early diagnosis and treatment than at a later stage of the disease.

Leukoplakia of the oral mucosa is a potentially malignant disorder, which means that there is an elevated risk oftransformation into a squamous cell carcinoma. The term oral leukoplakia is a clinical diagnosis for a predominantly white lesion which is not immediately recognizable as another well definable lesion which is white in appearance. Oral leukoplakia is generally an asymptomatic disorder of the mucosa with a prevalence of less than 2 per cent in the adult population. Tobacco usage is considered to be the most important etiological factor. Malignant transformation into a squamous cell carcinoma occurs in about I per cent per year. A patient with oral leukoplakia is generally referred to an oral and maxillofacial surgeon, who takes a biopsy for a definitive histopathological diagnosis. The outcome of the histopathological study, which may vary from hyperkeratosis to invasive squamous cell carcinoma, will determine the treatment. It is preferable that every leukoplakia is removed to reduce the risk of malignant transformation. Long term follow-up is indicated. Follow-up may in some cases be performed by the general dental practitioner.

Since oral cancer can be considered to be a relatively rare disease, dental practitioners will only rarely be confronted with it. Nevertheless, dental practitioners have a key role to play in the early diagnosis and referral to an oral and maxillofacial surgeon. The major part of oral cancers are squamous cell carcinomas, recognizable during routine oral inspection. Early referral is essential since treatment of small, not yet metastasized cancers have the best chance of long-term disease-free survival. Moreover, oral carcinoma is often preceded by white and/or red pre-malignant lesions of the salivary glands. These can similarly be detected by routine inspection. Here too, dentists play an important role in recognizing such diseases and referring patients to an oral and maxillofacial surgeon.

Recently, we reported the preliminary results of a prospective study on the possible premalignant character of oral lichen planus (OLP) and oral lichenoid lesions (OLL). Based on these data it was concluded that there was some but no convincing support for the hypothesis that patients with OLL have an increased risk of development of oral cancer, but not so in patients with OLP. In the present treatise the results of prolonged follow-up of this cohort of patients have been described. A study group of 192 patients, 67 patients diagnosed with OLP and 125 patients with OLL, according to revised World Health Organization diagnostic criteria, was followed for periods ranging from 7.6 to 96.9 months (mean, 55.9 months). The expected number of patients with oral cancer in the group of patients with OLP and in the group of patients with OLL was estimated by comparing the number of patients, their ages, sex, and the length of follow-up to annual incidence rates of oral cancer for the general population in The Netherlands. The binomial test was used to determine whether the observed number of cases of cancer in the OLP group and the OLL group exceeded the expected numbers. Four out of 192 patients, two men and two women, developed a squamous cell carcinoma of the oral mucosa during follow-up. All malignant transformations occurred in the OLL group. The malignant transformation of the OLL group, based on a mean follow-up of 53.8 months, was calculated at 0.71% per year. A comparison of the expected against actual figures for the development of carcinomas revealed no increase in patients with OLP and a 142-fold increase in patients with OLL, the latter being statistically significant, with a p-value of 0.044. The present data give support to the hypothesis that patients with OLL have an increased risk of development of oral cancer. There seems to be no increased risk in patients with OLP. In view of our results we advise to monitor only the subgroup of OLL patients twice a year for early detection of possible malignant transformation.

Introduction: Several authors have expressed the view that patients with oral lichen planus (OLP) are at increased risk of developing oral cancer. Since OLP cannot be effectively treated, regular screening for the possible development of oral cancer might be considered., Objectives: (i) To calculate costs and effectiveness of screening for oral cancer in OLP patients with a decision model; (ii) to compare the cost-effectiveness of different screening scenarios; and (iii) to perform a sensitivity analysis of several variables used in this model., Methods: Costs and effectiveness of a population of 100,000 OLP patients, being either screened or not screened for oral cancer, were calculated for the period of 1 year. Health gain was expressed as quality adjusted live years (QALY's) and equivalent lives saved (ELS). Cost-effectiveness was expressed as extra costs (costs of screening minus costs of no screening) per ELS. Then, the outcome was compared with the cost-effectiveness of a different screening scenario. Finally, the effect of varying the variables: (i) costs of cancer treatment; (ii) annual malignant transformation rate (MTR); (iii) sensitivity and specificity of an oral examination; and (iv) proportion of cancers found in stage I on extra costs per ELS were assessed in a sensitivity analysis., Results: The health gain from screening was 592 QALY's or the equivalent of 23.68 lives saved, costing 1,265,229 dollars, meaning that one ELS costed 53,430 dollars. Increase of cancer-treatment costs will significantly decrease the costs per ELS. When the MTR is lower than 0.4% per year, extra costs per ELS will increase exponentially. The effect of sensitivity and specificity of an oral examination in detecting oral cancer on cost-effectiveness seems to be substantial. When the proportion of cancers found in stage I can be increased from 40% (without screening) up to at least 60% after screening, extra costs per ELS will decrease exponentially., Conclusions: Screening for oral cancer in OLP patients, based on the presently used model, seems attractive. However, varying the several variables in the decision model has a significant impact on the final costs and effectiveness. Only, when additional information about these variables will become available, a more precise and realistic calculation can be performed.

Objective: Tobacco usage is the most important known aetiological factor in the development of oral leukoplakia. The purpose of this study was to investigate the possible relation of tobacco usage to the anatomical site of the leukoplakia., Subjects and Methods: Clinical data regarding tobacco usage and localisation of leukoplakia obtained from 166 patients with oral leukoplakia., Results: Leukoplakias in the floor of mouth appeared to be statistically significantly more often present in smokers than in non-smokers, compared to all other oral sites (P < 0.001; OR = 8.47 and 18.13 for men and women, respectively). On the contrary, leukoplakias on the borders of the tongue were statistically significantly more common among non-smokers, than smokers, compared to all other oral sites (P < 0.001; OR = 0.22 and 0.12 for men and women, respectively)., Conclusion: The present study suggests that the influence of tobacco on the development of leukoplakia varies by anatomical site.

A follow-up study of a hospital-based population of 166 patients with oral leukoplakia revealed a 2.9% annual malignant transformation rate. The median follow-up period was 29 months. Parameters associated with an increased risk of malignant transformation were female gender (P < 0.025), absence of smoking habits in women (P < 0.05), and a non-homogeneous clinical aspect (P = 0.01). For uniform reporting, a recently proposed classification and staging system has been used. Leukoplakias in stage IV, consisting of lesions with moderate or severe epithelial dysplasia, were associated with an increased risk of malignant transformation (P < 0.01). There were no oral subsites associated with an increased risk. Patients who had any form of intervention did not have a statistically significantly lower chance for malignant transformation than patients who were kept under surveillance without intervention.