There is still controversy as to the clinical findings and behavior of ameloblastic fibroma (AF). To clarify the exact biological profile, we critically re-evaluated the clinical characteristics of 31 cases of AF through a review of the Japanese literature. AF can be divided clinically into two distinct types: neoplastic AF (24 cases) and pericoronal hamartomatous AF (7 cases). The former appears as an expansive multilocular radiolucent lesion within the posterior mandible in the second decade. A recurrence rate of 13% was estimated. Its tendency to recur and to develop at ages beyond completion of odontogenesis clearly denotes a neoplastic nature. On the other hand, the latter appears as an asymptomatic small unilocular radiolucency over the occlusal surface of an unerupted mandibular molar primarily in the first decade. Neither persistent growth nor recurrence was observed. There is no proof that pericoronal AF sequentially progresses into a neoplastic AF. However, since two lesions are histologically indistinguishable, clinical findings have to be considered initially in a management plan of AF.

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To clarify the possible role of Langerhans cells (LCs) in oral verrucous carcinoma (OVC), LCs and anti-tumor immune cells in OVCs were immunohistochemically investigated with the use of anti-CD1a, 3, 4, 8, 68, and 79α antibodies. In OVCs, mucosa adjacent to OVCs, and normal oral mucosa, most intraepithelial CD1a-positive LCs were located in parabasal regions. Subepithelial LCs were scatteredly throughout the lamina propria. The densities of intraepithelial and subepithelial CD1a-positive LCs in OVCs were significantly higher than those in adjacent mucosa or normal oral mucosa. The density of CD1a-positive LCs in T3 stage OVCs was slightly lower than those in T1 and T2 stage OVCs. The majority of infiltrating CD3-, CD4-, and CD8-positive T lymphocytes, CD79α-positive B lymphocytes, and CD68-positive macrophages were observed in subepithelial portions of OVCs, but scattered CD3-, CD4-, and CD8-positive T lymphocytes were observed in intraepithelial portions of OVCs. CD8-positive T lymphocytes were more numerous than CD4-positive T lymphocytes in subepithelial portions of OVCs. In mucosa adjacent to OVCs and in normal oral mucosa, infiltration by CD3-, CD4-, and CD8-positive T lymphocytes, CD79α-positive B lymphocytes, and CD68-positive macrophages was minimal in both intraepithelial and subepithelial regions. LCs were slightly more numerous in CD8-positive T-cell dominant OVCs than in CD4-positive T-cell dominant OVCs. These results suggest that CD1a-positive LCs are related to CD8-positive T lymphocytes and that CD1a-positive LCs play a role in the anti-tumor immune response in OVCs.

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Fourteen patients with oral chronic graft-versus-host disease (GVHD) who received allogenic bone marrow transplantation were clinically and histopathologically studied. Most patients had lichenoid lesions on the oral mucosa and xerostomia. Two patients displayed multiple superficial mucoceles of the buccal mucosa as vesicular lesions. These clinical features resembled those of autoimmune diseases, such as lichen planus and Sjögren's syndrome. Histopathologically, all cases showed oral mucosal and minor salivary gland involvement characteristic of chronic GVHD, irrespective of the presence or absence of systemic lesions. The oral mucosa showed subepithelial lymphocytic infiltration with epithelial recessive changes, and the minor salivary glands displayed inflammatory changes or fibrosis with destructive alteration of epithelial cells. Immunohistochemically, CD3-positive cells were more numerous than CD79α-positive cells in the oral mucosa, while CD3- and CD79α-positive cells were equally observed in the minor salivary glands. CD4- and CD8-positive cells were detected equally in both the oral mucosa and the minor salivary glands. CD1a- and CD68-positive cells were scattered throughout the oral mucosa and the minor salivary glands. Cellular and humoral immune systems may differ between the oral mucosa and salivary glands in patients with chronic GVHD. CD1a- and CD68-positive cells may play a role in antigen presentation in oral lesions involved in chronic GVHD.

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Myoepithelioma with collagenous crystalloids occurring in the sublingual gland is described. A 40-year-old woman was admitted because of an enlarging swelling in the right side of the oral floor. Intraoral examination and magnetic resonance images revealed a localized tumorous lesion in the sublingual region. The lesion was diagnosed as pleomorphic adenoma on biopsy and was surgically excised. Histopathological examination of the tumor revealed the proliferating polygonal and spindle-shaped cells with a stroma of fibrous connective tissue. Radially arranged needle-shaped collagenous crystalloids were scattered throughout the stroma. The tumor cells were immunoreactive with cytokeratin, vimentin, muscle-specific actin, smooth muscle actin, and S-100 protein. Collagenous crystalloids were strongly positive for type III collagen immunostaining, and were ultrastructurally composed of electron-dense fibrillar materials transitional to collagenous fibers. On X-ray microanalysis, the crystalloids showed upregulation of sulfur, which was richly contained in type III collagen. These results suggest that type III collagen is involved in the formation of collagenous crystalloids.

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This report describes a 77-year-old Japanese male with anaplastic large cell lymphoma (ALCL) in the oral mucosa. He first noticed an ulcerated nodule on the tongue in July 1995. The biopsy specimen showed a non-specific inflammatory reaction and the ulcerated lesion regressed spontaneously. A similar lesion developed at a site posterior to the previous lesion two months later and the lesion disappeared again. A biopsy from the ulcerated nodule, which developed in the dorsum of the tongue in November 1995, demonstrated the atypical cells. Tumor cells showed a CD45+, CD3+, CD30+ and p80NPM/ALK+ phenotype. The lesion was diagnosed as ALCL with a T-cell phenotype, and clinical staging determined it to be stage IE. The tumor underwent spontaneous regression. In May 1998, multiple ulcers recurred in the oral cavity. Biopsies proved ALCL. Thereafter, additional ulcers developed in the oral cavity; however, biopsies were not performed. All of these lesions disappeared spontaneously.

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A 23 year-old male was pathologically examined post mortem at Tokyo Medical and Dental University. The patient died of circulation failure after a long state of cerebral death due to ventricular fibrillation. Myxomatous degeneration of the medial tunic and irregular hyperplasia of the intima were observed. These types of degenerations are observed as pathohistologic changes of Marfan syndrome (MFS), which is characterized by the systemic degeneration of elastic tissues caused by FBN1 gene mutation. We performed immunohistochemistry of FBN1 protein (fibrillin1) and found its downregulation in the vascular tissues. Cloning and sequencing of FBN1 gene revealed a point mutation in exon 27, which will make a substitution of protein sequence from proline to glycine. This mutation could alter elastic fiber stability and might have affected the conformation of vascular tissues of the patient.

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