The term “benign fibro-osseous lesions” covers a group of benign jaw-facial bone lesions; including fibrous dysplasia, osseous dysplasia and ossifying fibroma as well as their subgroups. All of these lesions show remarkable histologic similarity and distinction can only be made in the light of detailed clinical and radiologic findings. Because treatment procedures and prognoses are different for each group, proper diagnoses are necessary. The aim of this study was a comparative investigation of the proliferation potential of different lesions within the category of benign fibro-osseous lesions. We studied 35 cases of BFOL and 15 cases of similar long bone lesions to immunohistochemically determine their Ki-67 expression. Ki-67 expression was very rare for all of the BFOL. Our results suggest that there are no meaningful differences in the proliferation potentials of various benign fibro-osseous lesions. Ki-67 expression does not provide useful information for helping to distinguish these lesions.

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To characterize lateral periodontal cyst (LPC) clinicopathologically, we have analyzed 23 cases of LPC filed in Niigata University Hospital in the last 13 years. They accounted 1.4% of jaw cysts (1,683 cases total). The mean age of the patients was 46 years, and there were 13 male (56.5%) and 10 female (43.5%) patients. Maxillary LPCs were found in the incisor region, and mandibular ones were in the molar region. The maxillary cysts had larger size (19.8 mm, average diameter) and more frequent association with tooth roots (80%) than mandibular cysts (13.4 mm, 20%, respectively). Histopathologically, the linings of LPC were non-keratinized stratified squamous epithelia with occasional cuboidal changes containing small numbers of mucous or sebaceous cells. The base line of the lining epithelium was flat without rete processes. There were characteristic epithelial plaques (0.5 mm mean wide and 0.13 mm high) in all of the cases examined, and round or irregular-shaped epithelial islands were occasionally found in the cyst wall (34.8%). Immunohistochemically, there were scarcely any Ki-67-positive (+) cells in the lining epithelia, indicating that the lining cells were not proliferative. Both upper surface cells and basal cells of the epithelial plaques were CK19+ and integrin β1+, indicating that the epithelial plaques represented certain wrinkle or wavy protrusions of the inner surface of the cyst wall. The histopathological diagnosis of LPC must be precisely done from now on such clinicopathological characteristics are well recognized in this study.

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We report a case of oral ulceration that occurred during the course of rheumatoid arthritis treated with methotrexate. The patient was a 71-year-old man with oral ulceration of the floor of the mouth. The ulcer showed no induration, with a flat, clean surface and no bleeding. Biopsy revealed ulcer formation with marked inflammatory cell infiltration in the submucosa and dysplasia-like changes in epithelium. Topical steroids were ineffective. After reducing the dose of methotrexate, we observed that the lesion had epithelialized. The oral toxicity of low-dose methotrexate therapy is discussed.

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