Detection of oral cancer and oral potentially malignant disorders using artificial intelligence-based image analysis.

BACKGROUND: We aimed to construct an artificial intelligence-based model for detecting oral cancer and dysplastic leukoplakia using oral cavity images captured with a single-lens reflex camera. SUBJECTS AND METHODS: We used 1043 images of lesions from 424 patients with oral squamous cell carcinoma (OSCC), leukoplakia, and other oral mucosal diseases. An object detection model was constructed using a Single Shot Multibox Detector to detect oral diseases and their locations using images. The model was trained using 523 images of oral cancer, and its performance was evaluated using images of oral cancer (n = 66), leukoplakia (n = 49), and other oral diseases (n = 405). RESULTS: For the detection of only OSCC versus OSCC and leukoplakia, the model demonstrated a sensitivity of 93.9% versus 83.7%, a negative predictive value of 98.8% versus 94.5%, and a specificity of 81.2% versus 81.2%. CONCLUSIONS: Our proposed model is a potential diagnostic tool for oral diseases.

Primary Oral Mixed Neuroendocrine-Non-neuroendocrine Neoplasm (MiNEN): A Rare Case Report and Review of the Literature.

Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are rare tumors recently characterized by the presence of both neuroendocrine and non-neuroendocrine components within the same tumor tissue. Although MiNEN found their place in the WHO classification for various organs, this composite tumor in the head and neck region remains exceptionally rare. We present a case of primary oral MiNEN in a 64-year-old male located on the left side of lower gingiva. Biopsy raised suspicion of neuroendocrine carcinoma (NEC) and the patient underwent partial mandibulectomy. The resected specimen showed two distinct components of NEC and squamous cell carcinoma (SCC) with the confirmation of immunohistochemical markers. There has been no sign of recurrence nor metastasis 6 years after the surgery. In addition, we have conducted a review of published cases with potential relevance to this entity, resulting in five cases. The diverse terminology reinforces the need for a standardized classification system of oral/head and neck MiNENs.

Immunoexpression of SIRT1, 6, and 7 in oral leukoplakia and oral squamous cell carcinoma.

Sirtuins (SIRTs) are a family of proteins involved in the metabolic process responsible for extending the lifespan. The role of SIRT1, 6, and 7 in oral squamous cell carcinoma (OSCC) and oral leukoplakia (OLP), one of its precursors, is still elusive. In this study, 82 OLP and 77 OSCC were immunohistochemically examined for SIRT1, 6, and 7. Stained sections were thoroughly scanned and evaluated using a digital image analysis program. The SIRT1, 6, and 7 expressions were detected in the nuclei of epithelial and carcinoma cells in various degrees. Afterward, any correlations among SIRTs, including associations with clinicopathological features and the Kaplan-Meier curves were analyzed. OSCC demonstrated significantly higher SIRT1 expression than OLP, while non-dysplastic lesions showed significantly higher SIRT6 expression than other lesions. A strong correlation was observed between SIRT6 and 7 in OLP, SIRT1 and 6 in in OSCC and in SIRT6 and 7 when all lesion types were considered. There were no significant differences between SIRTs reactivity and the clinical features in OLP. For OSCC, SIRT1 and 6 was found to be directly associated with site of the lesion, while SIRT7 showed a direct relationship between gender, stromal lymphocytic infiltration, and depth of the invasion. OSCC with high SIRT7 expression revealed a slightly lower survival probability, although not statistically significant (p = 0.1019). Our findings suggest that SIRT1, 6, and 7 may play correlated and diverse roles in the development and advancement of OSCC.

Microvascular reconstruction for oral cancer in older adult patients: the impact of age on surgical outcomes.

OBJECTIVE: Flap complications continue to be a challenge in microsurgical reconstruction for older adults. We aimed to evaluate the impact of age on surgical outcomes after microvascular reconstruction. STUDY DESIGN: We retrospectively investigated 103 patients with oral squamous cell carcinoma who had undergone microvascular reconstruction surgery to compare microsurgical reconstruction, common postoperative complications, and flap success rates in geriatric (>75 years) and non-geriatric (<75 years) patients. We also evaluated differences based on the American Society of Anesthesiologists Physical Status score. RESULTS: We found no significant differences between the geriatric and non-geriatric groups in peri-operative, postoperative, or general complications. Conversely, we found that delirium and aspiration pneumonia were significantly more likely to occur in geriatric patients and that multiple medical complications were significantly more likely to occur in geriatric patients with a high American Society of Anesthesiologists score. CONCLUSION: Microvascular reconstruction can be performed effectively and without excessive complications in geriatric patients, and age should not be considered a contraindication for this procedure. Comorbidities play a stronger role in the prediction of adverse events.

Myeloid-derived suppressor cells and plasmacytoid dendritic cells are associated with oncogenesis of oral squamous cell carcinoma.

Myeloid-derived suppressor cells (MDSCs) help establish the tumor microenvironment by suppressing T-cell response in tumor-bearing hosts. Plasmacytoid dendritic cells (pDCs) activate antigen-specific T cells, thereby, maximizing their antitumor effects. IDO1 is associated with both MDSCs and pDCs and plays a major role in the formation of the tumor-mediated immunosuppressive environment. We utilized immunohistochemistry to examine the involvement of IDO1 in oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMDs, precancerous lesions). We examined the expression of MDSC markers, CD11b and CD33, as well as pDC markers, CD303 and IDO1, in 60 OSCC and 45 precancerous lesion specimens and analyzed their association with clinicopathological parameters. Expression of these biomarkers identifying MDSCs and pDCs was high in precancerous lesions in patients with severe dysplasia and OSCC. While detecting pDCs, high CD303 and IDO1 expression levels were frequently observed in moderately or poorly differentiated OSCCs. CD11b, CD33, and CD303 levels were significantly correlated with the mode of invasion; CD33 was correlated with OSCC invasion depth while the other three markers tended to be highly expressed in superficial cancer cases showing microinvasion. Expression levels of all four biomarkers were significantly associated with the cancerization of OPMDs to OSCCs. We show, for the first time, that the infiltration of MDSCs and pDCs is significantly associated with progression of premalignant lesions to OSCC. This suggests that these cells may act as prognostic biomarkers for premalignant lesion progression and that immunotherapeutic approaches that control each of these immunosuppressive cells may protect against progression to malignancy.

Pulmonary pleomorphic carcinoma metastasizing to the anterior mandibular gingiva: A case report and literature review.

INTRODUCTION AND IMPORTANCE: Pulmonary pleomorphic carcinoma (PPC) is a rare subtype of non-small cell lung cancer. No standard therapy has been established for advanced disease, which results in poor prognosis. Some cases of PPC metastasizing to mandibular gingiva have been reported, and the involved site in these reports is all unilateral mandible. CASE PRESENTATION: We report a case of PPC metastasizing to the anterior mandibular gingiva in a 68-year-old man. The patient was referred to our hospital with tumor bleeding and difficulty with intake. One month before, he had been diagnosed as PPC. The size of oral tumor was 28 × 25 mm, and we performed surgical resection. Although there was no recurrence of oral lesion, he died of systemic metastases after 3 months since the surgery. CLINICAL DISCUSSION: The prognosis of patients with metastatic tumor in oral region is poor. Radical treatment for oral lesion is often difficult due to the existence of other metastasis or the refractory, in particular cases with high grade malignancies such as PPC. On the other hand, because of the development of cancer treatment and the arrival of super-aging society, the number of patients with metastatic tumor in oral region has been expected to increase in future. CONCLUSION: PPC metastasizing to the gingiva of mandibular symphysis is extremely rare. If there are possibilities to improve the prognosis or quality of life, radical or palliative treatment for metastatic tumor in oral region should be performed.

Teriparatide with Octacalcium Phosphate Collagen Composite Stimulates Osteogenic Factors.

Octacalcium phosphate and collagen composite (OCPcol) promotes osteogenic differentiation and angiogenesis, thereby enhancing bone regeneration. Although a newly developed freeze-dried composite of OCPcol and teriparatide (OCPcolTPTD) reinforced bone regeneration more than OCPcol, the mechanism of bone regeneration remains unresolved. In this study, disks containing OCPcolTPTD, OCPcol, or ß-tricalcium phosphate (ß-TCP) col were inserted into rodents with calvarial bone defects, before euthanasia 4 weeks later. Immunohistochemical and histochemical analyses were performed on bone samples to evaluate bone matrix development, angiogenesis, and osteoclast and osteoblast localization. In the OCPcolTPTD and OCPcol groups, bone regeneration was observed at the surface of calvarial dura mater and around acidophilic granular cells with abundant collagenous fiber-containing cells. Furthermore, the newly formed bone in the OCPcolTPTD group showed a larger total area and individual separated area than the other groups. Various osteogenic proteins were detected in the regenerated bone and peri-bone tissues by histochemistry and immunohistochemistry. Although the expression of several osteogenic biomarkers in the OCPcolTPTD group after 4 weeks of implantation was significantly lower than that in the OCPcol group, new bone formation by OCPcolTPTD in the center of the defect, where bone regeneration is difficult, tended to be superior to that by OCPcol. These results suggest that OCPcolTPTD enhanced bone regeneration more evenly and homogenously than OCPcol. Impact statement Our study suggests that octacalcium phosphate and collagen (OCPcol) together with a TPTD enhances bone regeneration in rodents with calvarial bone defects. Furthermore, we believe that composite of OCPcol and teriparatide (OCPcolTPTD) could be developed into novel clinical technique for the regeneration or repair of bone.

Comparison of different diagnostic imaging techniques for the detection of bone invasion in oral cancers.

OBJECTIVES: To evaluate the ability of different imaging modalities to accurately detect bone invasion in oral squamous cell carcinomas. PATIENTS AND METHODS: Patients with oral squamous cell carcinoma, who were scheduled for mandibulectomy or maxillectomy, underwent clinical evaluation using five preoperative imaging diagnosis methods-contrast-enhanced MRI, CT, 99mTc scintigraphy (Tc scan), FDG-PET CT (PET/CT), and panoramic radiography. The sensitivity and specificity of each modality in detecting bone invasion were calculated by comparing the findings on the images with postoperative histopathological findings. In a subgroup of patients, we further assessed the ability of MRI and CT to detect the accurate extent of bone invasion, including the height, width, and depth in patients with pathological mandibular invasion. RESULTS: Overall, 50 patients were enrolled in this study, and nine patients with pathological mandibular invasion were included in our subgroup analysis. MRI was found to be the most useful method in detecting bone invasion, showing the highest sensitivity (88.9%) and negative predictive values (92.3%). CT (87.5% specificity and 77.8% sensitivity) was more specific than MRI, though less sensitive. Combined PET/CT was more sensitive (83.3%) and less specific (71.9%) than CT. Tc scan had high sensitivity (88.9%); however, the specificity was relatively low (71.9%). CONCLUSION: MRI was the most useful method in detecting bone invasion. A negative MRI result definitively excludes bone marrow invasion. In patients with positive MRI findings, a negative CT may be useful in ruling out bone marrow invasion.

Wound healing effect of autologous fibrin glue and polyglycolic acid sheets in a rat back skin defect model.

Fibrin glue from autologous plasma may prevent viral infection and allergic reaction. Moreover, this biomaterial contains growth factors such as TGF-ß and VEGF that promote reconstruction of the mucous membrane by stimulating fibroblast proliferation and angiogenesis. Thus, autologous fibrin glue is predicted to improve healing better than commercial fibrin glue. Here, we evaluated the effects of autologous fibrin glue on the crucial early phase of wound healing. Epithelial defects were introduced in rats and covered with polyglycolic acid (PGA) sheets with or without commercial or autologous fibrin glue. Wound healing was assessed for six weeks by histology and immunohistochemistry. Our results demonstrate that wounds covered with PGA sheets and autologous fibrin glue achieved efficient wound healing without complications such as local infection or incomplete healing. The rate of recovery of the regenerating epithelium in this group was superior to that in wounds covered with PGA sheets and commercial fibrin glue. Immunohistochemistry of laminin, cytokeratin, and VEGF confirmed fine and rapid epithelial neogenesis. Collectively, our results indicate that covering surgical wounds with autologous fibrin glue promotes wound healing and epithelialization, improves safety, and reduces the risks of viral infection and allergic reaction associated with conventional techniques.

Mandible fractures and dental injuries related to road traffic accidents over a 12-year period-Retrospective multicentre study.

BACKGROUND/AIM: Road traffic accidents (RTAs) are a common cause of maxillofacial injuries. The aim of this retrospective multicentre study was to investigate the characteristics of maxillofacial fractures and dental injuries that occurred in RTAs in Miyagi, Japan. MATERIALS AND METHODS: The records of 404 patients with maxillofacial injuries treated at the Oral and Maxillofacial Surgery Departments of four different institutions over a period of 12 years were analysed. Ninety-nine of these patients had suffered these injuries in an RTA. RTA-related cases were divided according to age, gender, presentation month, presentation day of the week, transportation mode, time of accident, fracture sites and fracture mechanism. RESULTS: There were 72 males and 27 females who suffered injuries as the result of an RTA, for a male-to-female ratio of 2.7:1.0, with a mean age of 35.3 years (range, 1-86 years old). Most of the accidents occurred in June and on a Wednesday, and most of the affected patients were riding a bicycle at the time. The number of patients with maxillofacial injuries related to bicycle riding showed an increasing trend in recent years. Mandible fractures were the most prevalent, followed by dental injuries and maxilla fractures. In cases with a single fracture of the mandible, the symphysis was the most frequent site, while in those with multiple fractures, the association of symphysis and bi-lateral condyle fractures was the greatest. For bicycle-related accidents, a single fracture in the mandible occurred more often than multiple fractures. CONCLUSIONS: The number of RTA-related injuries while bicycle riding showed an increasing trend with mandible fractures commonly seen in those cases. Efforts to reduce maxillofacial injuries related to bicycle accidents are needed.

Immunohistochemical assessment of Eph/ephrin expression in oral squamous cell carcinoma and precursor lesions.

To evaluate erythropoietin-producing hepatocellular carcinoma (Eph)/Eph receptor-interaction protein (ephrin) expression in oral squamous cell carcinoma (OSCC) and oral epithelial precursor lesions (OEPLs), EphA2, EphB4, and ephrinB2 were examined and compared with microvessel density (MVD) and lymphatic vessel density (LVD). Samples from 73 OSCC and 43 OEPLs patients were immunohistochemically analyzed with antibodies against EphA2, EphB4, ephrinB2, CD34, and D2-40. Results were compared with clinicopathological findings. Immunohistochemical reactivity for EphA2, EphB4, and ephrinB2 was detected in epithelial cells and some stromal vascular cells in OEPLs and OSCC, proportionately with the level of malignancy. The number of blood vessel endothelial cells stained with CD34 and lymphatic vessel endothelial cells stained with D2-40 was increased in OEPLs and OSCC. In OSCC, ephrinB2 and EphB4 exhibited significant correlation with recurrence and invasion depth, respectively. MVD was significantly lower in slight lymphocytic reaction than in prominent stromal reaction. Association was found between LVD and T classification, postoperative metastasis, survival, mode of invasion, and invasion depth. Expression of EphA2, EphB4, ephrinB2, MVD, and LVD might be associated with malignant potential of the oral epithelium. Angiogenesis and lymphangiogenesis appear to be related to progression of potentially malignant oral lesions.

Octacalcium phosphate collagen composite stimulates the expression and activity of osteogenic factors to promote bone regeneration.

OBJECTIVE: This study investigated the bone regenerative properties of an octacalcium phosphate collagen composite (OCP/Col) in a rat calvarial bone defect model. DESIGN: An OCP/Col or ß-tricalcium phosphate (ß-TCP)/Col disk was implanted into the critical-sized calvarial defects and fixed 2 or 4 weeks later. The radiopacity of defects was examined after disk implantation by the radiographic examination and micro-computed tomography (µ-CT). Immunohistochemical and histochemical analyses were carried out to assess the bone matrix maturation, neovascularization, and osteoclast and osteoblast distribution in the neonatal bone. RESULTS: Radiographic and µ-CT examination of the area of implanted OCP/Col indicated the newly formed bone and no difference from those of the original bone. Osteopontin, osteocalcin, Runt-related transcription factor 2, type 1 collagen, vascular endothelial growth factor, and alkaline phosphatase or tartrate-resistant acid phosphatase in the newly formed calvarial bone and the surrounding connective tissue were detected by immunohistochemistry and histochemistry. Biomarker expression was not significantly elevated at the defect site; the area of which was calculated by dividing the distance from the healthy bone margin or calvarium and dura mater surface. There was no difference in the expression of these biomarkers in the OCP/Col group at 2 and 4 weeks after surgery. In addition, the expression levels of all markers were higher in the OCP/Col group than in the ß-TCP/Col group at 2 and 4 weeks after surgery. CONCLUSIONS: The OCP/Col as a bone regeneration material not only exhibits osteoconductive activity that is dependent on residual healthy bone tissue, but also has osteoinductive capacity, which promotes angiogenesis and osteogenic cell invasion from host tissue into the bone defect.

Immunohistochemical assessment of chromatin licensing and DNA replication factor 1, geminin, and γ-H2A.X in oral epithelial precursor lesions and squamous cell carcinoma.

BACKGROUND: Carcinogenesis occurs when the cell cycle is compromised. Chromatin licensing and DNA replication factor 1, geminin, and γ-H2A histone family member X are expressed in cells in G1 phase, S/G2 /M phases, and apoptosis, respectively, and these three markers may be useful for histological evaluation of malignant lesions. Here, we aimed to identify cell cycle phases and apoptosis using immunohistochemistry in oral epithelial precursor lesions and oral squamous cell carcinoma. METHODS: Chromatin licensing and DNA replication factor 1, geminin, and γ-H2A histone family member X expression levels were immunohistochemically examined in tissue specimens from 55 patients with oral epithelial precursor lesions and 50 patients with oral squamous cell carcinoma. Associations of clinicopathological variables with marker expression were assessed. RESULTS: Chromatin licensing and DNA replication factor 1 was expressed in the prickle cell layer of oral epithelial precursor lesions and many carcinoma cells of oral squamous cell carcinoma. Geminin reactivity was widely distributed in high-grade dysplasia and oral squamous cell carcinoma rather than low-grade or no dysplastic cases. γ-H2A histone family member X was expressed in the superficial layer of oral epithelial precursor lesions and scattered carcinoma cells of oral squamous cell carcinoma. In oral squamous cell carcinoma, lower geminin expression was observed in recurrent cases. Geminin and γ-H2A histone family member X were associated with the degree of differentiation and mode of invasion. CONCLUSION: Chromatin licensing and DNA replication factor 1, geminin, and γ-H2A histone family member X expression levels were correlated with oral carcinogenesis; these markers were associated with clinicopathological behaviors in oral squamous cell carcinoma.

Expression of immunoregulatory molecules PD-L1 and PD-1 in oral cancer and precancerous lesions: A cohort study of Japanese patients.

OBJECTIVE: An association of the programmed cell death-1 (PD-1) and its ligand PD-L1 with various types of malignant tumors has been established. This study aimed to investigate the role of the PD-L1/PD-1 pathway in oral squamous cell carcinoma (OSCC) and oral epithelial precursor lesions (OEPL). MATERIALS AND METHODS: We examined 106 OSCC and 79 OEPL specimens for PD-L1 and PD-1 expression by immunohistochemistry. The results were compared with clinicopathological features of OSCC patients. RESULTS: In OSCC and OEPL specimens, PD-L1 expression was detected predominantly in epithelial or carcinoma cells, whereas PD-1 expression was found mainly in infiltrating or stromal lymphocytes. Seventy-two OSCC (67.9%) and 21 OEPL (26.6%) specimens were positive for PD-L1, and 73 OSCC (68.9%) and 23 OEPL (29.2%) specimens were positive for PD-1. PD-L1 and PD-1 expression levels were significantly different between OEPL and OSCC specimens (P < 0.001). There were significant positive correlations between PD-L1 and PD-1 expression in OEPL and OSCC specimens (P < 0.001). PD-L1 and PD-1 immunoreactivity was significantly associated with tumor size (P < 0.05). PD-L1 and PD-1 immunoreactivity in cases with advanced TNM staging was significantly higher than that in low staging cases (P < 0.01). There were significant correlations between PD-L1 and PD-1 expression in OSCC specimens and pathological variables such as stromal lymphocytic reaction (P < 0.05) and invasion depth (P < 0.01). CONCLUSION: PD-L1 and PD-1 immunohistochemical status may be related to carcinogenesis, tumor progression, and prognosis in oral epithelial lesions. Agents targeting PD-1 and PD-L1 might be useful for OSCC treatment.

Do Mandibular Third Molars Play a Role in Fractures of the Mandibular Angle and Condyle?

INTRODUCTION: The relationship between impacted mandibular third molars with angle and condylar fractures is subject of many publications, yet their conclusions differ widely, hence the authors wanted to investigate this topic in their patients. METHODS: The authors designed a retrospective study including 241 patients who presented with angle and/or mandibular condyle fractures over a 13-year period at the authors' institution. The study variable was the presence/absence of third molars. The authors used the Pell and Gregory system to classify their position, whereas the angulation was classified using Archer classification. The outcome variables were the presence of angle and condylar fractures. Other study variables included fracture etiology. RESULTS: Assaults were the most frequent cause of angle fractures (62.7%), whereas falls were mostly responsible for condylar fractures (79.6%). Angle fractures were mostly isolated (66.3%), whereas condylar fractures were mostly associated with other fractures (62.6%). The majority of the angle fractures occurred in patients with third molars (63.6%), on the contrary the majority of the condylar fractures occurred in patients without mandibular third molars (78.3%). Angle fractures were mostly associated with fully erupted or superficially impacted third molars (90,9%). Finally in the presence of mesioangulated third molars, condylar fractures did not happen in 83.8% of patients. CONCLUSIONS: According to the authors' findings, fully erupted or superficially impacted mandibular third molars are a risk factor for angle fractures but at the same time a protective factor for the condyle. On the contrary, the absence of mandibular third molars "strengthens" the angle and represents a risk factor for condylar fractures.

Clinical evaluations of complete autologous fibrin glue, produced by the CryoSeal® FS system, and polyglycolic acid sheets as wound coverings after oral surgery.

The CryoSeal® FS System has been recently introduced as an automated device for the production of complete fibrin glue from autologous plasma, rather than from pool allogenic or cattle blood, to prevent viral infection and allergic reaction. We evaluated the effectiveness of complete autologous fibrin glue and polyglycolic acid (PGA) sheet wound coverings in mucosa defect oral surgery. Postoperative pain, scar contracture, ingestion, tongue dyskinesia, and postoperative bleeding were evaluated in 12 patients who underwent oral (including the tongue) mucosa excision, and received a PGA sheet and an autologous fibrin glue covering. They were compared with 12 patients who received a PGA sheet and commercial allogenic fibrin glue. All cases in the complete autologous fibrin glue group demonstrated good wound healing without complications such as local infection or incomplete cure. All evaluated clinical measures in this group were similar or superior to the commercial allogenic fibrin glue group. Coagulation and adhesion quality achieved with this method was comparable to that with a PGA sheet and commercial fibrin glue. Covering oral surgery wounds with complete autologous fibrin glue produced by an automated device was convenient, safe, and reduced the risk of viral infection and allergic reaction associated with conventional techniques.

Clinical evaluations of autologous fibrin glue and polyglycolic acid sheets as oral surgical wound coverings after partial glossectomy.

Polyglycolic acid (PGA) sheets and commercial fibrin glue are commonly used to cover open wound surfaces in oral surgery. Compared to commercial fibrin glue composed of pooled allogeneic blood, autologous fibrin glue is less expensive and poses lower risks of viral infection and allergic reaction. Here, we evaluated postoperative pain, scar contracture, ingestion, tongue dyskinesia, and postoperative bleeding in 24 patients who underwent partial glossectomy plus the application of a PGA sheet and an autologous fibrin glue covering (autologous group) versus 11 patients in whom a PGA sheet and commercial fibrin glue were used (allogeneic group). The evaluated clinical measures were nearly identical in both groups. Remarkable wound surface granulation was recognized in two cases in the autologous group. No complications were observed in either group, including viral infection or allergic reaction. Abnormal postoperative bleeding in the wound region was observed in one case in the allogeneic group. Coagulation and adhesion of the autologous fibrin glue were equivalent to those of conventional therapy with a PGA sheet and commercial fibrin glue. Thus, our results show that covering wounds with autologous fibrin glue and PGA sheets may help avoid the risks of viral infection and allergic reaction in partial glossectomy cases.

Detection of human papillomavirus infection in oral squamous cell carcinoma: a cohort study of Japanese patients.

OBJECTIVE: Recent evidence suggests that human papillomavirus (HPV)-related head and neck squamous cell carcinoma (HNSCC) is a separate HNSCC subgroup with distinct epidemiology, histopathological characteristics, therapeutic response to chemotherapy and radiation, and clinical outcome. This study aimed to investigate the role of HPV infection in oral squamous cell carcinoma (OSCC) and the correlation between HPV infection, tumor suppressor protein p16 expression, and clinicopathological features in Japanese patients. METHODS: In total, 174 OSCC specimens were examined for p16 levels by immunohistochemistry, and p16-positive OSCCs were analyzed for HPV DNA by in situ hybridization (ISH) and HPV genotypes by real-time PCR. The results were evaluated for the association with clinicopathological characteristics of OSCC patients. RESULTS: Twenty-four OSCC samples were found positive for p16 expression; all of them were well-differentiated tumors. P16 immunoreactivity was significantly associated with the invasion depth and tended to correlate with sex, site in the oral cavity, stromal reaction, TNM stage, and survival. HPV DNA was detected in 13 of 24 (54%) p16-positive OSCC by real-time PCR; HPV 16, 18, and other high-risk genotypes were the most prevalent. However, ISH failed to detect HPV DNA in p16-positive OSCCs. CONCLUSION: P16 immunoreactivity and HPV genotyping by real-time PCR may be useful markers of HPV infection in OSCC. However, although HPV-related OSCC showed good outcomes, HPV infection may have a minor role in oral oncogenesis in Japanese patients.