OLP is a chronic inflammatory disease with refractory dyskeratosis and is one of the most frequent oral mucosal diseases [10–13]. Although several studies have been conducted on OLP, the etiology is unknown and treatment can be difficult . OLP is more common in middle-aged and older women in their 40s to 60s, with a male-to-female ratio of approximately 1:2 to 1:3. In this study, the ratio of males to females was 1:2.1, and more than half of the patients were in their 60s or 70s, indicating that OLP was more prevalent in older individuals in this study. The reason for the high prevalence of OLP in women is unclear; however, some reports have shown little or no sexual predilection [9, 14]. These results should be interpreted after considering the possibility that many male patients have latent OLP and do not have the opportunity to be examined because of regional bias or lack of time for hospital visits because of work. In addition, Japan has a large aging population and is expected to become a “super-aged” society in the future. With the extension of healthy life expectancy and longer life expectancy of women, the prolonged duration of the disease will pose a risk for carcinogenesis, which is a major issue.
The subjective symptoms of this lesion include mild pain, contact and irritation pain, burning sensation, and discomfort of the oral mucosa. In general, unpleasant symptoms, such as irritation, contact pain, and burning sensation, are observed in approximately half of the patients [14, 15]. In addition, it has been reported that approximately 30% of the patients without clear symptoms of discomfort present to the hospitals because they are motivated by mass media reports or were aware of some abnormality, such as a feeling of coarseness . Currently, the speed of information dissemination through the Internet and media is remarkably fast, and patients can easily obtain medical information, including correct and incorrect information. The differential diagnosis of this disease from cancer and precancerous lesions is important. From the viewpoint of preventive medicine, there is a need to further educate both medical professionals and the public. In this study, approximately half of the patients had no subjective symptoms and were examined only for the purpose of diagnosis as they visited our department for a thorough examination. More than half of the patients presented at an early disease stage, within one month of the onset of symptoms, while others visited more than one year after the onset of symptoms.
The most frequent site of OLP in the oral cavity is the cheek mucosa (approximately 35%), followed by the gingiva and tongue, while the palate is relatively rarely affected [2–4, 6–7, 15, 16]. Some reports have classified the location of the lesions into the buccal mucosa and gingiva in a broad sense, although they are often found mainly at the gingiva–buccal mucosa transition area. These lesions usually persist for a long period  and are affected by the state of the periodontal tissues. Therefore, in this study, the gingiva–buccal mucosa transition area was included in the classification according to the location. The results showed that the most common site was the buccal mucosa, followed by the alveolar gingiva, gingiva–buccal mucosa transition area, tongue, and intrinsic buccal mucosa to gingiva–buccal mucosa transition area. Bilateral lesions were found in 57.7% of cases, with a mean lesion size of 2.1 cm, indicating multiple lesions, a trend consistent with those of previous reports [3, 8, 15, 16]. The most common form of OLP is a typical lace-like white patch on the buccal mucosa with surrounding redness, which is relatively easy to distinguish. However, OLP lesions on the gingiva and tongue may be modified by secondary infections or irritation from teeth or prosthetic materials, making them difficult to differentiate.
There are several clinico-visual classifications of OLP lesions, including the Andreasen classification , Silverman's classification , and Einsen's classification . It is important that the classification is consistent among the evaluators and is easy and reliable for the diagnosis of a wide range of mixed lesions. In this study, the Andreasen classification, which has several classification items and is widely used for external validity, was used . In this study, as in other reports, the reticular type was the most common, followed by the erosive type . Comparing the chief complaint with the type classification of clinical visual examination, the reticular type is generally less symptomatic than the other types. The atrophic, erythematous, erosive, and ulcerative types tend to be associated with more unpleasant symptoms, such as contact pain, than the reticular and hyperkeratotic types . Several other studies have reported similar results, with cases involving ulcers and erosions being symptomatic [18–23]. However, the issues with the classification of clinical visual types vary according to the reports of each institution, there are no clear diagnostic criteria, and the reproducibility and agreement among institutions and diagnosticians are not always high. OLP, especially the reticular type, can be easily diagnosed by the naked eye. However, several other lesions, such as leukoplakia, erythroplakia, and epithelioid type, show findings similar to those of OLP, and unified diagnostic criteria have not been developed to distinguish these lesions. Histopathological examination is essential for the definitive diagnosis of OLP. However, many institutions diagnose clinical OLP based on gross examination and palpation and do not perform a biopsy. In a review of cases clinically diagnosed as OLP, biopsy was performed in 35.8% of cases, and it is thought that cases that are relatively easy to diagnose clinically, such as the reticular type, are less problematic. In a report on the concordance of pathological diagnosis with clinical diagnosis of OLP, the concordance rate was reported to be approximately 50–80% [7, 17, 24–27]. In this study, cytological diagnosis was performed in 91 cases (73.4%) and biopsy was performed in 48 (38.7%); the percentage of cases where biopsy was performed was equivalent to that reported by other studies. It is important to detect malignancy early in the treatment and follow-up of this disease, and it is necessary for the surgeon to decide whether to use cytology for simplicity or biopsy for definitive diagnosis. In addition, clinical and pathological diagnoses are often inconsistent, and technical problems are encountered during biopsy, such as the inability to obtain a reliable pathological diagnosis because the biopsy was performed at a site with poor tissue response rather than at the site of the main lesion. OLP has been reported to undergo malignant transformation, and although the mechanism of malignant transformation is unknown, it has been suggested that increased inflammatory cytokines may be involved . The clinical classification of malignant lesions has been reported to be erosive or erythematous . Therefore, in cases of erosive or atrophic lesions, biopsy at the time of initial diagnosis and shorter follow-up intervals are necessary. In all cases of malignant transformation, clinical findings, such as enlargement of erythema and worsening of contact pain, were observed during the follow-up from the initial diagnosis to malignant transformation [12, 28–32]. Biopsy should be performed when morphological and color changes or clinical symptoms appear during the follow-up.
In our department, OLP is treated with oral hygiene instructions and follow-up, and local steroid therapy is initiated when clinical symptoms, such as spontaneous pain, appear. If a fungal infection is detected, antifungal drugs are administered, and steroid ointment is discontinued until no fungal infection is detected. In this study, the effectiveness of steroid ointment in improving symptoms in patients with OLP was evaluated. The use of steroid ointment was found to improve symptoms in all but erosive and papular lesions. It is desirable to evaluate symptom improvement using objective indices, such as a sign score  or visual analog scale (VAS). However, it has been reported that the size of the lesion does not correlate with the intensity of subjective symptoms and that the validity of VAS evaluation is questionable because of its large variability . This study used subjective and visual changes of the lesion as criteria for judging improvement by treatment . Furthermore, the improvement of the lesions based on the patient's awareness and change in the appearance of lesions on visual examination were evaluated. In a previous study on the treatment effect of the clinical examination type of the lesions, there was no difference in the treatment effect on reticular, erosive, and atrophic lesions, the treatment effect in mixed reticular-erosive lesions was poor, and the lesions were more resistant to treatment than other types . In this study, steroid ointment did not improve symptoms in the erosive and plaque-shaped lesions but was somewhat successful in other types. This may have been because of the extent and size of the erosions and abrasion caused by the positional relationship between the teeth and prosthesis.
This study has some limitations. It involved a retrospective analysis of data from a single facility. Furthermore, the sample size used in this study was not sufficient. OLP may be associated with Candida infection, which may reduce the efficacy of topical steroid application; however, this was not investigated in this study. However, the number of cases of the atrophic, papular, plaque-like, and bullous forms of lichen planus evaluated in this study was small, and more cases should be included future studies.