Oral lichen planus (OLP) is classified into 3 major types: plaque (PLA), reticular (RET), and atrophic (ATR). This study was designed to examine the clinical and histopathological characteristics of these three types of OLP in the buccal mucosa. A total of 375 specimens of OLP (20 PLA, 20 RET, and 20 ATR) and normal buccal mucosal (NBM) were examined histopathologically. Epithelial thickness was less in ART and RET than in NBM. Epithelial thickness in RET was greater than in ATR. Mean numbers of PCNA-positive cells and CD1a-positive cells in the covering epithelium were higher in RET and PLA than in ATR and NBM. PLA, RET, and ATR types of OLP have different histopathological characteristics. Differences among these types might reflect distinct stages of disease.

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Adenomatoid odontogenic tumor (AOT) is an uncommon entity of odontogenic origin, characterized by the formation of duct-like structures in the tumor. Although its histogenesis is still uncertain, it is also considered to be a rather hamartoma-like lesion. Here we report a case of AOT in a 22-year-old Japanese woman, the first documented case to have been analyzed for the presence of hard α-keratin (human hair protein). A positive reaction for human hair proteins was noted in the marginal area of calcified material, or at the interface or between areas of dystrophic calcification and columnar epithelial cells. Furthermore, melanin pigment was demonstrated histologically in this case, similar to several previously reported cases of AOT with melanin. This is the first reported case of AOT with hard α-keratin. These findings suggest that AOT may have the potential to differentiate into hair components.

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Epithelioid hemangioendothelioma (EHE) is a rare malignant vascular tumor that typically involves the soft tissues, skin, viscera, bone, and, in rare cases, the oral cavity. Two extremely rare cases of EHE arising in the tongue of two young children are reported. One case developed as a solitary nodule on the lateral border of the tongue of a one-year-old boy, and the other case developed as multiple discrete small nodules on the dorsum of the tongue of a 3-year-old girl. The tumors were composed of epithelioid eosinophilic cells with intracytoplasmic vacuoles containing erythrocytes. Vascular differentiation of the tumors was confirmed by immunohistochemistry for such endothelial markers as CD31, von Willebrand factor, and Ulex europaeus agglutinin type I lectin (UEA-I) binding. Both cases were treated by wide local excision and showed no local recurrence during their long follow-up period. In conclusion, EHE can develop in very young children and can present itself as multiple intraoral lesions.

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Salivary gland tumors commonly occur as a single focus in one salivary gland. Warthin tumor often arises in bilateral parotid glands, and the membranous type of basal cell adenoma frequently occurs in unilateral parotid glands. We describe herein a case of extremely rare synchronous double solid type basal cell adenoma arising in the left parotid glands in a 49-year-old woman. This case was treated with surgical enucleation, and no signs of recurrence have been seen as of 4 years 3 months after surgery.

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Follicular dendritic cell sarcoma (FDCS) is a tumor of recent description that is frequently misdiagnosed because of its rarity and diverse histologic patterns. We herein present a case of FDCS of the pharyngeal region in a 62-year-old man. This case possessed histological features similar to those of Wegener's granulomatosis and NK/T cell lymphoma. A panel of antibodies was applied to help differential diagnoses for other possible lesions. Tumor cells were characterized by their immunoreactivity, i.e., CD21(+), CD23(+), CD35(+), and CD68(-). We also survey the clinical features and prognosis of 28 FDCS cases of the oronasopharyngeal region previously published.

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