Aggressive osteoblastoma of the mandible.

We report a case of aggressive osteoblastoma of the mandible, an extremely rare primary bone tumor of the maxillofacial skeleton. Although osteoblastomas are benign tumors requiring only curettage for cure, there is a small subset of tumors that exhibit locally aggressive behavior and have atypical histopathologic features. Differentiation from low-grade osteosarcoma is often difficult. There is some disagreement as to the proper classification of these tumors. The correct diagnosis must be based on clinical, radiographic and pathologic features. Surgical resection and reconstruction is the recommended treatment for these invasive lesions.

Altered hippocampal-prefrontal activation in HIV patients during episodic memory encoding.

OBJECTIVE: To investigate the integrity of hippocampal-prefrontal circuitry during episodic encoding in patients with HIV. METHODS: Functional MRI was used to observe changes in blood oxygenation level-dependent (BOLD) signal in 14 HIV-positive participants and 14 age- and education-matched control subjects while performing an episodic encoding task. Subjects also completed neuropsychological measures of attention and memory. RESULTS: Behavioral results revealed no significant differences in neuropsychological performance. The fMRI results revealed that while both groups recruited brain regions known to be important for successful encoding, including bilateral medial temporal lobes and inferior prefrontal gyri, the HIV group demonstrated significantly reduced signal intensity changes in the right posterior hippocampus, right inferior frontal gyrus, and left lingual gyrus. Additionally, the HIV group exhibited more activity within lateral frontal and posterior parietal regions. CONCLUSIONS: This study demonstrates altered integrity of hippocampal-prefrontal regions during episodic encoding in HIV-positive patients. These results extend previous studies that have documented the effects of HIV on fronto-striatal circuits, and suggest the virus functionally impacts the hippocampal system as well.

Premalignant oral mucosal diseases.

A premalignant phase in the development of oral cancer is predicted by the classic model of experimental epithelial carcinogenesis. Virtually all oral squamous cell carcinomas arise from a premalignant precursor, but it is difficult to specifically define the term premalignant. Oral pathologists use the term epithelial dysplasia to indicate microscopic features in a biopsy specimen that are associated with a risk of malignant change and then assign a grade of severity. There is good correlation between higher grades of dysplasia and increasing risk of cancer but less so with the lower grades. The clinical appearances manifested by oral epithelial dysplasia and early oral cancer include leukoplakia, erythroplakia, and speckled leukoplakia. This paper discusses and illustrates these clinical lesions, their associated risk factors, their relationship to epithelial dysplasia, and the associated risk of evolution into oral cancer.

Oral cancer: a self-assessment quiz.

This article consists of a quiz on oral cancer knowledge. The goals of the quiz are to reinforce known cancer information and present new information. Photographs are used to bring a sense of the practical problems that clinical pathology presents. Also, a number of real-life case situations are presented with their corresponding illustrations so that the readers may use their clinical judgment and experience in choosing an answer.

Differential effects of damage within the hippocampal region on memory for a natural, nonspatial Odor-Odor Association.

Debate continues on whether the role of rodent hippocampus in memory is limited to the spatial domain. Recently, this controversy has been addressed with studies on the social transmission of food preference, an odor-odor association task with no spatial requirements. Multiple reports have concluded that damage to the hippocampal region impairs memory in this task, but there remain questions about the extent of damage essential to produce an impairment. Furthermore, a recent study () found no effect of hippocampal lesions on memory in this task. We tested animals with complete lesions of the hippocampus (H) lesions of the hippocampus plus subiculum (HS), and lesions of the adjacent, anatomically related cortices of the parahippocampal region (PHR). H lesions produced an impairment on spatial delayed alternation, but not on memory for the social transmission of food preference, whereas HS and PHR lesions produced severe and equivalent impairments on memory for the socially acquired food preference. We discuss possible explanations for the discrepancy with the results of and conclude that the hippocampus and subiculum together play a critical role in the formation of this form of nonspatial, relational memory.

Benign epithelial odontogenic tumors.

Teeth are formed from a complex interaction of primitive ectoderm and ectomesenchymal tissues. Because humans develop 2 sets of teeth (deciduous and permanent), odontogenesis is a prolonged biologic process. Residues of odontogenic tissues are present in most humans- both during and after odontogenesis. These elements may be found in either bone or soft tissue of the jaws and may contribute to the formation of odontogenic tumors in these sites. Further, the mixture of epithelium and mesenchyme necessary for tooth formation allows for the development of tumors composed of either element or for mixed neoplasms. This article discusses 4 of the 5 benign odontogenic neoplasms that are of epithelial origin and offers an agreed on classification scheme, which includes important clinicopathological subtypes. Specifically discussed are ameloblastoma, calcifying epithelial odontogenic tumor (Pindborg tumor), adenomatoid odontogenic tumor, and squamous odontogenic tumor. A brief history of each tumor is given along with a discussion of demographic data, clinical findings, radiographic features, and gross features where useful. A thorough discussion is presented of diagnostic histopathology including histologic variants. Generally accepted modes of therapy and follow-up recommendations are discussed.

Oral mucosal melanomas: the WESTOP Banff workshop proceedings. Western Society of Teachers of Oral Pathology.

A workshop to discuss primary oral melanomas was convened at the annual Western Society of Teachers of Oral Pathology meeting in Bannf, Alberta, Canada. Fifty oral melanomas, identified from the files of the participants, were reviewed in order to better understand the clinical features, histologic spectrum, and natural history of these perplexing lesions. Results confirmed that oral melanomas occur in adults almost three times more frequently in men than women and have a decided predilection for the palate and gingiva. Some lesions exhibit a clinically detectable and prolonged in situ growth phase, whereas others seem to lack this property and exhibit only or predominantly invasive characteristics. Recurrences, metastases, and death from tumor were characteristic of the follow-up of a limited number of patients. Until definitive prospective data are collected that elucidate natural history, oral mucosal melanomas should be tracked separately from cutaneous lesions. All oral pigmented lesions that are not clinically diagnostic should be biopsied. Lesions with equivocal histopathologic features might be referred to as "atypical melanocytic proliferation" and should be excised. Recognition of lesions in an early in situ phase and aggressive treatment should have a favorable effect on prognosis. To enhance future or prospective study of these rare neoplasms, guidelines for reporting oral melanomas are suggested.

Types of optometric testing emphasized in different practice modes.

BACKGROUND: In order to determine if tests performed in an examination vary with practice settings, we surveyed all 5,200 California licensed optometrists and asked them to identify their primary mode of practice and the percentage of time and/or frequency that certain test procedures were done in an eye examination. METHODS: We restricted our analysis to three practice modes: private, corporate, and nonprofit/health maintenance organization (NP/HMO). We received a 66.4 percent response rate. To determine any trends in emphasis of testing by the three practice modes and to establish relationships between the three, we compared each mode of practice to the other. The combinations were private vs. corporate, corporate vs. NP/HMO, and private vs. NP/HMO. The three combinations were compared to the frequency of performing case history, stereo acuity testing, binocular vision testing, biomicroscopy, dilated fundus examination, tonometry and perimetry. RESULTS AND CONCLUSIONS: We found the following relationships in the frequency/emphasis of testing as statistically significant: 1) For stereopsis testing: private practices performed it more often than corporate; 2) For binocular vision testing: private practices performed it more than did either corporate or NP/HMO, corporate performed it more than NP/HMO; 3) For tonometry: corporate performed it slightly more than NP/HMO; 4) For dilation: NP/HMO performed it more than both private and corporate; and 5) For perimetry: private performed it more than both corporate and NP/HMO.

Human ameloblastoma tumors express the amelogenin gene.

Instructive signals are responsible for the regulation of the expression of gene products characteristic of many cell lineages during normal development and potentially during neoplasia. The odontogenic origin of ameloblastomas is based largely on the similarity in histologic appearance between the tumor and the developing tooth organ. A pathognomonic pattern for odontogenic tissue-specific gene expression in ameloblastomas has not been previously shown. In these studies, the gene expression parameters for human ameloblastomas have been characterized with the techniques of messenger RNA phenotyping in combination with Northern and in situ hybridization analysis of messenger RNA. The results of these studies confirm that amelogenin, a gene transcribed solely by differentiated ameloblasts, was expressed by epithelial cells from human ameloblastomas. This observation suggests that the instructive signals required for ameloblast differentiation are shared during normal development and tumorigenesis of odontogenic epithelium.

Disruption of synchrony between parasite growth and host cell division is a determinant of differentiation to the merozoite in Theileria annulata.

The multinucleated macroschizont stage of the protozoon Theileria annulata is an intracellular parasite of bovine leukocytes. The parasite induces the host cell to proliferate, and divides in synchrony with the immortalised host cell. Differentiation to the next stage occurs within the host cell culminating in the release of merozoites and destruction of the leukocyte. In this study clones of Theileria annulata macroschizont-infected cell lines were isolated by limiting dilution and tested for differentiation to the merozoite stage (merogony). Two cloned cell lines underwent differentiation with enhanced efficiency, while two others were of lower efficiency. Quantification was carried out using monoclonal antibodies, which showed that over 90% of the cells in an enhanced cloned cell line could be induced to differentiate. By carrying out induction at 41 degrees C for limited periods of time followed by culture at 37 degrees C evidence was obtained that differentiation to the merozoite is a two-step process: a preliminary reversible phase, followed by a second irreversible phase of differentiation. Analysis of the nuclear number of the macroschizont and the growth rate of the cloned cell lines showed that the ability to differentiate was associated with an increase in nuclear number (size) of the macroschizont, generated by a disruption in the synchrony between parasite growth and host cell division. We believe that these results reveal a relationship between a reduction in parasite division and differentiation, and that there are similarities between stage differentiation in parasites and cellular differentiation in higher eukaryotes.

Central odontogenic fibroma: clinicopathologic features of 19 cases and review of the literature.

The odontogenic fibroma is a benign neoplasm infrequently reported in the literature (20 cases). Nineteen additional examples are reported. This lesion occurs most frequently in the maxilla anterior to the molars and displays a striking female predilection. On occasion, it may be associated with an unerupted mandibular third molar. Histomorphologically, it is not encapsulated. A spectrum of fibrous connective tissue stroma is present: from myxoid to densely hyalinized and from relatively acellular to cellular. Calcification may or may not be present. It is distinguished by the presence of sparse cords and islands of inactive odontogenic epithelium. Enucleation or surgical curettage is appropriate therapy and recurrence is low. As there appears to be no correlation of histologic pattern with clinical behavior, it seems unnecessary to try to separate the tumor into two variants.