We studied 1809 patients with oral cancer who visited and were treated, in 2002, at the 148 institutions certified as training facilities by the Japanese Society of Oral and Maxillofacial Surgeons. Of these institutions, 39 are dental university hospitals, 44 are medical university hospitals, 64 are general hospitals, and for 1 institution, the classification was not known. The patients consisted of 1071 (59.2%) males and 738 (40.8%) females (male: female ratio, 1.45:1), who had a average age of 65.2 years. The tongue (40.2%) was the most common site affected, followed by the gingiva (32.7%), buccal mucosa (10.1%), and oral floor (9.0%). There were 6 cases of multiple intraoral cancers. On histopathological examinations, squamous cell carcinoma (88.7%) was the most common type found, followed by adenoid cystic carcinoma (2.1%), and mucoepidermoid carcinoma (1.7%). Cases classified as T2N0 were the most common (32.1%), followed by T1N0 (21.4%), T4N0 (8.0%), and T2N1 (7.6%). Distant metastasis occurred in 17 patients (1.0%). Nonepithelial tumors, among which malignant melanoma was the most common type, accounted for 1.8% of the tumors. The sizes of the nonepithelial malignant tumors ranged from 1.0 to 7.0 cm, with an average size of 3.7 cm.

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BackgroundMycoplasmas are the smallest free-living organisms; Mycoplasma salivarium and Mycoplasma orale are the most common species isolated from the oropharynx. Oral leukoplakia is the most prevalent potentially malignant disorder of the oral mucosa; its etiology has not been defined. Our previous study with DNA-binding fluorescent dye suggested the presence of mycoplasmas in the epithelial cells of leukoplakia tissue.ObjectiveOur aim was to detect M. salivarium in the epithelial cells of leukoplakia by immunohistochemistry.DesignWe produced a polyclonal antibody (PAb) reactive to Mycoplasma by injecting a rabbit with M. salivarium cells (ATCC 23064) mixed with complete Freund's adjuvant and a monoclonal antibody specific to M. salivarium by injecting M. salivarium cells (ATCC 23557) mixed with complete Freund's adjuvant into the footpads of a rat. Then, we attempted to detect M. salivarium in the epithelium of leukoplakia tissues by immunohistochemistry.ResultsWe obtained an antimycoplasma rabbit PAb reactive to all seven Mycoplasma species used in this study. Three hybridoma clones producing monoclonal antibodies specific to M. salivarium were obtained, and an M. salivarium-specific monoclonal antibody, designated 7-6H, was established. Immunohistochemistry with these antibodies revealed M. salivarium in the epithelial cells of leukoplakia with hyperplasia and hyperkeratosis on histology. PCR and sequencing verified the presence of M. salivariumDNA in the epithelial cells of leukoplakia.ConclusionIntracellular M. salivarium was identified in the epithelial cells of leukoplakia.

BackgroundOral lichen planus (OLP) is a T‐cell‐mediated inflammatory disease; however, its exact etiology is unknown. Hyperkeratosis is often observed in OLP lesions. Previous studies have revealed the localization of Mycoplasma salivarium in the epithelial cells of oral leukoplakia with hyperkeratosis. Herein, we investigated the presence of M. salivarium in OLP tissue by immunohistochemistry to determine the causative factor of OLP.MethodsForty‐one formalin‐fixed, paraffin‐embedded samples obtained from 31 patients with OLP were examined. Ten samples of normal‐appearing oral mucosa were used as controls. Immunohistochemistry (IHC) was performed using anti‐M. salivarium monoclonal antibodies.Results and Conclusions Mycoplasma salivarium was detected in the epithelium and lymphocyte infiltrate area in 24 of 41 OLP samples (58.5%). The bacteria were intracellularly localized in epithelial cells, while it was unclear whether they were also localized in lymphocyte cells or in the extracellular spaces among the lymphocytes in the subepithelial lymphocyte infiltrate area. Little or no staining was observed in the epithelium in the normal‐appearing mucosa samples. Sawtooth rete ridge formation was observed in 21 OLP samples (51.2%), and a significant positive correlation between sawtooth rete ridge formation and IHC positivity was demonstrated. However, the role of M. salivarium in the epithelium and lamina propria of OLP tissue remains unknown.