Immunohistochemical demonstration of epithelial glutathione S-transferase isoenzymes in normal, benign, premalignant and malignant human oral mucosa

The expression and localization of glutathione S-transferase (GST) isoenzymes in the epithelium of normal oral mucosa ( n = 9), overlying reactive fibrous hyperplasia ( n =9), and of potentially malignant [leukoplakia ( n =25), submucous fibrosis ( n =12), verrucous hyperplasia ( n =16)] and malignant [squamous cell carcinoma ( n =36), verrucous carcinoma ( n =13)] oral lesions were examined immunohistochemically using polyclonal antibodies raised against GST isoenzymes (alpha, mu and pi) with the standard avidin-biotin-peroxidase complex (ABC) method. GST alpha, mu and pi were almost completely absent in the epithelium of normal oral mucosa and overlying benign fibrous tissues. GST alpha staining was cytoplasmic and focally positive, while GST mu staining was similar to but weaker than that seen for GST alpha. GST pi showed both cytoplasmic and nuclear staining and was expressed in 60% of leukoplakias with mild dysplasia ( n =15), 80% of leukoplakias with moderate to severe dysplasia ( n =10). 75% of submucous fibrosis samples ( n =12), 75% of verrucous hyperplasias ( n =16), 77% of verrucous carcinomas ( n =13), 81% of well-differentiated squamous cell carcinomas ( n = 26) and 70% of moderate- to poorly-differentiated squamous cell carcinomas ( n =10). In addition, GST pi expression was independent of the state of differentiation of oral cancers. Since GST pi was significantly over-expressed in the oral premalignant and malignant lesions, the kinetics of GST pi-positive cells and the value of GST pi as a tumor marker in oral carcinogenesis need further investigation.     

Human papillomavirus as a risk factor in oral carcinogenesis: a study using in situ hybridization with signal amplification

Introduction:  It is still controversial whether human papillomavirus (HPV) can be considered a risk factor in oral carcinogenesis. The aim of this study was to detect HPV DNA in 50 cases diagnosed as oral leukoplakias, with different degrees of epithelial dysplasia, and as oral squamous cell carcinomas, using in situ hybridization with signal amplification (CSA-ISH).
Methods:  HPV DNA was assessed in paraffin sections using CSA-ISH with a wide-spectrum biotinylated DNA probe. In HPV-positive cases, genotyping with specific probes to HPV types 6/11, 16/18 and 31/33 was performed.
Results:  The overall prevalence of HPV infection was 24%, markedly higher than that found in the control group. Results showed a discrete proportional relationship in the indices found in leukoplakia with no dysplasia, leukoplakia with dysplasia, and squamous cell carcinoma, but this was not statistically significant. When separating the group of leukoplakia by degrees of dysplasia, this relation of proportion was not observed. In genotyping, HPV types 16/18 were the most prevalent, and types 6/11 were only found in groups of mild or no dysplasia.
Conclusion:  The results suggest that HPV is not likely to play a role in the progression of malignant transformation in oral lesions. Nevertheless, the increased prevalence of HPV infection compared to normal oral mucosa and the fact that high-risk HPV types were the most frequently identified do not allow the exclusion of HPV as a risk factor in oral carcinogenesis.     

Epstein-Barr virus in tobacco-induced oral cancers and oral lesions in patients from India

D'Costa J, Saranath D, Sanghvi V, Mehta AR: Epstein-Barr virus in tobacco-induced oral cancers and oral lesions in patients from India. J Oral Pathol Med 1998; 27: 78–82. © Munksgaard, 1998.
We examined 103 oral squamous cell carcinomas (OSCC), 100 oral lesions consisting primarily of leukoplakia (82 cases), and 76 clinically normal mucosa specimens from the contralateral site in the oral cavity of individuals with oral lesions, for the presence of Epstein-Barr virus (EBV). Polymerase chain reaction (PCR) was used to amplify a 239 bp fragment of the BamHIL region of the EBV genome, followed by Southern blot hybridization with EBV oligonucleotide probe to increase further the specificity and sensitivity of the assay system. Since EBV seropositivity is frequent in populations, we also examined the peripheral blood cells (PBC) from 141 patients (50 oral cancer patients, 91 patients with oral lesions) for the presence of EBV We detected EBV in 25 of 103 (25%) OSCC, 13 of 100 (13%) oral lesions, 3 of 76 (4%) clinically normal mucosa samples and 10 of 141 (7%) PBC. Our results indicate that EBV may contribute as one of the multiple factors in oral cancers, in a certain proportion of Indian patients.     

Human papilloma virus (HPV) antigens and local immunologic reactivity in oral squamous cell tumors and hyperplasias

Abstract – A series of 191 oral mucosal tumors including those with suspected HPV (Human Papilloma Virus) etiology; squamous cell papilloma (SQP), condyloma acuminatum (CA), focal epithelial hyperplasia (FEH), as well as those regarded as unrelated to HPV; fibrous hyperplasia (FH), papillary hyperplasia (PH), and true fibroma (TF), were analyzed for HPV structural proteins (by indirect immunoperoxidase IP-PAP technique), for the presence of epithelial dysplasia, and for the cellular composition (B and T lymphocytes, mononuclear phagocytes, (MPS cells)) of their local inflammatory cell infiltrates using ANAE-(acid α-naphthyl acetate esterase) stain. HPV structural proteins were disclosed in 85% of FEH, in 75% of CA, and in 41 % of SQP. These three lesions significantly differed from PH and FH with regard to the intensity and cellular composition of the local infiltrates, being most intense and B cell predominated in the latter two. Mild dysplasia was found in 20% of both CA and SQP lesions, the former also showing moderate dysplasia in 12% of cases. The HPV antigen positivity was negatively correlated with dysplasia in CA and SQP, the intensity of the infiltrate showing positive association with dysplasia. The results are discussed in terms of HPV etiology of CA, SQP and FEH, of the host immunologic reactivity against these lesions, as well as of the possible role of HPV in human squamous cell carcinogenesis.     

Presence of human papilloma virus,herpes simplex virus and Epstein–Barr virus DNA in oral biopsies from Sudanese patients with regard to toombak use

J Oral Pathol Med (2010) 39 : 599–604 Using PCR/DNA sequencing, we investigated the prevalence of human papillomavirus (HPV), herpes simplex virus (HSV) and Epstein–Barr virus (EBV) DNA in brush biopsies obtained from 150 users of Sudanese snuff (toombak) and 25 non‐users of toombak in formalin‐fixed paraffin‐embedded tissue samples obtained from 31 patients with oral dysplasias (25 toombak users and 6 non‐users), and from 217 patients with oral cancers (145 toombak users and 72 non‐users). In the brush tissue samples from toombak users, HPV was detected in 60 (40%), HSV in 44 (29%) and EBV in 97 (65%) of the samples. The corresponding figures for the 25 samples from non‐users were 17 (68%) positive for HPV, 6 (24%) positive for HSV and 21 (84%) for EBV. The formalin‐fixed samples with oral dysplasias were all negative for HPV. In the 145 oral cancer samples from toombak users, HPV was detected in 39 (27%), HSV in 15 (10%) and EBV in 53 (37%) of the samples. The corresponding figures for the samples from non‐users were 15 (21%) positive for HPV, 5 (7%) for HSV and 16 (22%) for EBV. These findings illustrate that prevalence of HSV, HPV and EBV infections are common and may influence oral health and cancer development. It is not obvious that cancer risk is increased in infected toombak users. These observations warrant further studies involving toombak‐associated oral lesions, to uncover the possible mechanisms of these viral infections in the development of oral cancer, and the influence of toombak on these viruses.     

Proliferative verrucous leukoplakia: high incidence of gingival squamous cell carcinoma

BACKGROUND: Proliferative verrucous leukoplakia (PVL) is a multifocal and progressive lesion of the oral mucosa, often associated with papillomavirus, seen mainly in older females, and characterized by a high recurrence rate and high rate of transformation into verrucous or oral squamous cell carcinoma (OSCC). The aim of this study was to analyse the clinical characteristics of a substantial group of patients with PVL, evaluating the characteristics of those who developed cancer, and comparing them with a group of patients with OSCC but no preceding PVL. METHODS: A group of 30 patients with PVL was studied for the clinical aspects and characteristics, age, sex, location, recurrence, the appearance of new lesions, and the frequency of development of oral cancer. A disease control group was formed with 110 patients with OSCC chosen randomly from among those treated in the same Service in this period of time. The patients were grouped as PVL and no cancer (Group 1); PVL developing cancer (Group 2) and patients with OSCC without clinical lesions associated with PVL (Group 3). RESULTS: The average age of the PVL patients (Groups 1 and 2 combined) was 70.97 +/- 12.73 years, of which 80% were women. Only 23.3% were cigarette smokers. The area most frequently affected with PVL was the lower gingiva. Recurrence after treatment was seen in 86.7%, and new lesions appeared in 83.3%. Many (63.3%) developed cancer (Group 2). Comparison of Groups 2 and 3 patients showed that those with PVL developing cancer were more likely to develop gingival carcinoma and also to be older, more often females, and less likely to smoke tobacco. CONCLUSION: Cancer developing in patients with PVL manifested particularly on the gingiva.     

Human papillomavirus (HPV) DNA sequences in oral precancerous lesions and squamous cell carcinoma demonstrated by in situ hybridization

A series of routinely processed, paraffin-embedded biopsies from 73 surgically treated oral precancerous lesions (OPL) (22 cases), and oral squamous cell carcinomas (SCC) (51 cases), was first screened using an in situ DNA hybridization technique with a human papillomavirus (HPV) DNA probe cocktail containing the 35S-labelled DNA of HPV types 6, 11, 13, 16, 18 and 30. The specific HPV types in lesions shown to contain HPV DNA in this procedure were further analysed by using in situ hybridization and the 6 HPV DNA probes separately. A total of 12/73 (16.4%) of the lesions proved to contain HPV DNA; 6/51 (11.8%) carcinomas and 6/21 (28.6%) dysplasias. The most frequent sites of HPV DNA-positive lesions were palate (4/7; 57%), followed by the floor of the mouth (2/8; 25%), the tongue and gingiva (11.8%). HPV 13 or HPV 30 were not found in any of the lesions studied. HPV 11 DNA was demonstrated in 2 mild dysplasia lesions, but not in carcinomas. One additional mild dysplasia proved to contain HPV 6 DNA. HPV 16 DNA was present in 5 biopsies; 3 carcinomas and 2 dysplasias. In one of the HPV 16-positive carcinomas, HPV 18 DNA was simultaneously present. HPV 18 alone was found in 3 additional carcinomas and in one moderate dysplasia lesion. The results confirm the recently reported evidence on HPV involvement in OPL and oral cancer. The implications of these findings are discussed in terms of the possible HPV etiology of oral SCC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Outcomes of oral squamous cell carcinoma arising from oral epithelial dysplasia: rationale for monitoring premalignant oral lesions in a multidisciplinary clinic

Surveillance of oral epithelial dysplasia results in a number of newly diagnosed cases of oral squamous cell carcinoma (SCC). The clinical stage of oral SCC at diagnosis influences the magnitude of treatment required and the prognosis. We aimed to document the stage, treatment, and outcome of oral SCC that arose in patients who were being monitored for oral epithelial dysplasia in a dedicated multidisciplinary clinic. Those with histologically diagnosed lesions were enrolled on an ethically approved protocol and molecular biomarker study. Details of clinical and pathological TNM, operation, radiotherapy, recurrence, second primary tumour, and prognosis, were recorded in patients whose lesions underwent malignant transformation. Of the 91 patients reviewed (median follow-up 48 months, IQR 18-96), 23 (25%) had malignant transformation. All were presented to the multidisciplinary team with stage 1 disease (cT1N0M0). Of these, 21 were initially treated by wide local excision, 2 required resection of tumour and reconstruction, and 2 required adjuvant radiotherapy. At follow-up 3 had local recurrence, one had regional recurrence, one had metachronous lung cancer, and 5 had second primary oral SCC. There were further diagnoses of oral dysplasia in 5 during follow-up, and it is estimated that 76% of patients will have one or other event in 5 years. Disease-specific survival was 100% and overall survival was 96% (22/23). Median follow-up after diagnosis of oral SCC was 24 months (IQR 11-58). Specialist monitoring of oral epithelial dysplasia by a multidisciplinary team allows oral SCC to be detected at an early stage, and enables largely curative treatment with simple and usually minor surgical intervention. The high incidence of second primary oral SCC in high-risk patients with oral epithelial dysplasia further supports intensive targeted surveillance in this group.     

High risk human papillomavirus in oral squamous carcinoma: evidence of risk factors in a Venezuelan rural population. Preliminary report

In a search for the presence of human papillomavirus (HPV) and some etiologic cofactors in oral squamous cell carcinoma (OSCC), 50 women diagnosed as OSCC were analyzed by a multiplex polymerase chain reaction (PCR) assay specific for HPV types 6, 11, 16, and 18. This study revealed that 60% (30/50) of the OSCC patients were positive for HPV-DNA sequences. This group was analyzed according to smoking, alcohol consumption, number of pregnancies, poor oral health and low social economic status. The current results indicate an increased incidence of HPV malignant types in the oral cavity in women with OSCC. Also, they support a multifactorial model of oral cancer causation.     

Human papillomavirus (HPV) DNA sequences in oral precancerous lesions and squamous cell carcinoma demonstrated by in situ hybridization

A series of routinely processed, paraffin-embedded biopsies from 73 surgically treated oral precancerous lesions (OPL) (22 cases), and oral squamous cell carcinomas (SCC) (51 cases), was first screened using an in situ DNA hybridization technique with a human papillomavirus (HPV) DNA probe cocktail containing the 35S-labelled DNA of HPV types 6, 11, 13, 16, 18 and 30. The specific HPV types in lesions shown to contain HPV DNA in this procedure were further analysed by using in situ hybridization and the 6 HPV DNA probes separately. A total of 12/73 (16.4%) of the lesions proved to contain HPV DNA; 6/51 (11.8%) carcinomas and 6/21 (28.6%) dysplasias. The most frequent sites of HPV DNA-positive lesions were palate (4/7; 57%), followed by the floor of the mouth (2/8; 25%), the tongue and gingiva (11.8%). HPV 13 or HPV 30 were not found in any of the lesions studied. HPV 11 DNA was demonstrated in 2 mild dysplasia lesions, but not in carcinomas. One additional mild dysplasia proved to contain HPV 6 DNA. HPV 16 DNA was present in 5 biopsies; 3 carcinomas and 2 dysplasias. In one of the HPV 16-positive carcinomas, HPV 18 DNA was simultaneously present. HPV 18 alone was found in 3 additional carcinomas and in one moderate dysplasia lesion. The results confirm the recently reported evidence on HPV involvement in OPL and oral cancer. The implications of these findings are discussed in terms of the possible HPV etiology of oral SCC. The use of the in situ DNA hybridization as a powerful tool (enabling the localization of specific HPV DNA sequences and the proper classification of the lesion at the same site) in the study of routinely processed oral biopsies is strongly advocated.     

Loss of the adenomatous polyposis coli gene and human papillomavirus infection in oral carcinogenesis

Recent evidence suggests that loss of heterozygosity (LOH) of the adenomatous polyposis coli (APC) gene plays a role in colorectal tumorigenesis and other cancers. However, little is known as to whether the APC gene contributes to the pathogenesis of oral squamous cell carcinoma. To assess involvement of both the APC gene and the human papillomavirus (HPV) in the development of oral pre-malignant and malignant lesions, we analysed DNA from 14 paired oral normal and pre-malignant or malignant paraffin-embedded biopsy specimens, and DNA from cultured normal and HPV 16-immortalised oral epithelial cells for the presence of LOH of APC and for HPV infection, using PCR based techniques. LOH of APC occurred in 80% of cases of oral epithelial dysplasia, 67% of carcinoma in situ, 50% of invasive squamous cell carcinoma cases, and in the HPV 16-immortalised oral epithelial cells. HPV was detected in half of the biopsy specimens, with HPV 16 as the dominant type. More than half of the carcinoma cases were found to contain both LOH of APC and HPV infection. These results suggest that LOH of APC is an early event during oral tumorigenesis. Our findings also suggest a strong correlation between HPV infection, particularly HPV 16, and LOH of the APC gene in oral squamous cell carcinomas.     

Analysis of human papillomavirus DNA in oral squamous cell carcinomas

Evidence from several laboratories suggests that HPV plays a role in the etiology of squamous cell carcinomas of the oral cavity. A rnultifactorial risk factor profile for the development of oral cancer may include HPV in addition to well-established risk factors such as tobacco and alcohol use. The prevalence of oral carcinomas repotted to be associated with HPV has varied widely due to differences in the sensitivity of the assay used for HPV detection. The aims of this study were: (1) to ascertain the prevalence of HPV DNA in oral squamous cell carcinomas using the most sensitive technique available, the polymerase chain reaction; (2) to determine the type of HPV in the tumors; and 3) to correlate the virologic data with other risk factor data obtained from patients' records. Fourteen (78%) of 18 primary tumors, 6 (67%) of 9 normal epithelial tissues from the patients and 5 (100%) of 5 neck metastases were HPV DNA-positive. Of the 14 HPV DNA-positive primary tumors, specific typing revealed HPV 16 in 2, HPV 18 in 2, HPV 16 and IS in 5, HPV 6/11, 16 and 18 in 4, and HPV 6/11 in 1. HPV types in the normal or metaslatic tissue were usually the same as those in the respective primary tumor. There was no significant association between HPV presence and any of 12 factors or patient characteristics studied.     

Association of HPV infections with second primary tumors in early-staged oral cavity cancer

Oral Diseases (2012) 18 , 809–815 Objective: The infection of human papilloma virus (HPV) has been reported in head and neck cancer; however, the clinical significance of HPV infection on the pathogenesis of oral cavity squamous cell carcinoma (OSCC) is still uncertain. Materials and Methods: The study recruited 103 patients with pathological early‐stage OSCC between March 1997 and December 2003 from Chang Gung Memorial Hospital, Taiwan. Tumor specimens were HPV‐genotyped by the EasychipVR HPV Blot method. Clinical association study was performed by using chi‐square, Kaplan–Meier, and logrank tests. Results: Thirty‐one patients (30.1%) were positive for HPV infection. The most frequent HPV types were types 16 (16 patients, 51.6%) and 18 (seven patients, 22.6%). HPV infection was not associated with tumor aggressiveness (pathological tumor stage or differentiation status), risk exposure (alcohol, cigarette, or areca quid chewing habit), or the treatment outcome (disease‐free survival or overall survival). However, infection with HPV‐18 was associated with the occurrence of a second primary cancers (P = 0.033), indicating the infection of HPV in OSCC enhances the susceptibility of developing secondary malignancy. Conclusions: There are 30% of the patients with OSCC infected with HPV, with most high‐risk types. HPV‐18 infection may enhance the susceptibility of second primary tumors. Large scale of validation study will be needed to confirm this result.     

Human papillomavirus DMA in oral squamous cell carcinomas and normal mucosa

Human papillomavirus (HPV) infections in oral carcinomas and normal oral mucosa were studied by consensus primer screening and typing for HPV types 6/11,16 and 18 DNA. After polymerase chain reaction (PCR) the DNA species of interest were identified by Southern blot hybridization with digoxigenin-labeled oligonucleotide probes. Frozen tissue and scrapings were equally suitable for HPV testing and yielded high HPV detection rates in carcinomas. By comparison, HPV analysis of paraffin-embedded material was much less efficient. HPV were demonstrated in 61.5% (16/26) of oral squamous cell carcinomas, high risk HPV 16 and 18 being the preferential types. The frequency of HPV detection in non-neoplastic mucosa of tumor patients decreased clearly with increasing distance from the tumor (range 26.9–3.8%) suggesting focal HPV infections. In contrast, normal buccal mucosa of a group of healthy volunteers contained HPV DNA only in 1%(1/97).     

Detection of human papillomavirus DNA in oral mucosal lesions using in situ DNA-hybridization applied on paraffin sections

The in situ DNA hybridization technique, carried out under stringent conditions, was used to detect human papillomavirus (HPV) DNA of types 6, 11, and 16 in paraffin sections of 32 surgically treated oral mucosal lesions. Expression of HPV structural proteins was analyzed by means of the immunoperoxidase (IP-PAP) method. A total of 10 (31.3%) of the 32 lesions proved to express HPV antigens, which were found in 4 of 7 squamous cell papillomas, in 2 of 2 classic condylomas, in 2 of 10 papillary hyperplasias, and in 2 of 3 leukoplakia lesions. Two of the squamous cell papillomas contained HPV 6 DNA, and 4 additional lesions were positive for HPV 11 DNA. In one of the condylomas, a double infection by HPV 6 and 11 was found, while the second was positive for HPV 11 alone. Both the HPV antigen-positive papillary hyperplasias contained HPV 6 DNA, as did the HPV antigen-positive leukoplakia lesions. Of the latter, one was infected by HPV 6 and 11. DNA of the "high-risk" HPV 16 was contained in two lesions: one lichen planus lesion and one of the two squamous cell carcinomas. The results confirm the previously reported evidence of HPV involvement in oral mucosal lesions. The implications of these findings are discussed in terms of the well-established premalignant character of oral leukoplakia and oral lichen planus, although far less commonly versus leukoplakia, with special emphasis on the discovery of the "high-risk" HPV 16 in the latter as well as in oral cancer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Human papilloma virus: An etiological and prognostic factor for oral cancer?

The increasing prevalence of human papilloma virus (HPV)‐positive oral tumors can be considered an epidemic. Although the incidence of HPV cervical cancer is decreasing, the incidence of oral cavity and oropharyngeal cancers associated with HPV is increasing. The presence of certain HPV genotypes could be a predictor of future oral cancer lesions, although lesions associated with HPV could be less aggressive and exhibit a higher survival rate. In the present study, we review the most important biologic, clinic, epidemiologic, and prognostic factors associated with HPV infection and oral cancer.     

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.     

In situ DNA hybridization analysis of oral papillomas, leukoplakias, and carcinomas for human papillomavirus.

Twenty-one papillomas, 23 ordinary benign keratoses, 13 smokeless tobacco keratoses, 10 verrucous hyperplasias, 10 verrucous carcinomas, 17 squamous cell carcinomas, 3 epithelial dysplasias, and 6 lichen planus lesions were evaluated for human papillomavirus (HPV) types 6/11, 16/18, and 31/33/35, with biotinylated double-stranded DNA probes by in situ hybridization. Sixty-two percent (13/21) of oral squamous papillomas were positive for HPV DNA. HPV DNA types 6 and 11 demonstrated the strongest reactivity. Of the 13 cases, 10 also showed some reactivity with HPV-16/18 and -31/33/35. None of the cases of keratoses, epithelial dysplasia, squamous cell carcinoma, verrucous hyperplasia, verrucous carcinoma, or lichen planus were positive for HPV DNA. This study confirms the consistent and frequent finding of HPV DNA in oral squamous cell papillomas and the inconsistency of being able to identify HPV DNA in keratotic, premalignant, or cancerous lesions of the oral mucous membranes.     

Expression of p16 in oral cancer and premalignant lesions

Background:  Expression of p16 has been proposed as a marker for malignant transformation. This study aimed to evaluate p16 expression in oral squamous cell carcinoma (OSCC) and premalignant lesions including oral leukoplakia (OL) with and without dysplasia.
Methods:  Expression of p16 was investigated in 56 samples including OSCC, OL with and without dysplasia, and normal oral mucosa. Expression of p16 was identified by immunohistochemistry, using the CINtecTM p16INK4a Histology Kit. Both nuclear and/or cytoplasmic staining of the keratinocytes were considered to be positive and the percentage of positive cells was calculated.
Results:  Expression of p16 was detected in 3/16 (18.75%) cases of OSCC, in 4/15 (26.7%) cases of OL without dysplasia, and in none of OL with dysplasia and normal mucosa. No significant differences in p16 expression prevalence were found among OSCC, OL with and without dysplasia and normal mucosa. The percentages of positive cells in OSCC and OL without dysplasia were 0.89 and 0.17, respectively. No significant difference in the percentage of positive keratinocytes was found.
Conclusion:  As a marker, p16 is not reliable for oral mucosal dysplasia and malignant transformation.