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Background: Myofibromas are rare benign neoplasms composed of myoid cells and myofibroblasts. This study aimed to systematically review case reports and a series of myofibromas (MF) and myofibromatosis (MFT) occurring in the oral and maxillofacial regions in order to describe their main clinicopathological features. Methods: This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. Electronic searches were conducted in 2023 in four databases: MEDLINE/PubMed, Web of Science, Scopus, and EMBASE. A manual search and a search in the grey literature were also conducted. The lesions were classified as MF or MFT according to their original report. Results: A total of 169 cases were included in this systematic review. Men were slightly more affected, with a painless nodule. When occurring in soft tissue, MF usually developed in the gingiva (mean age:29.23 ± 21.93 years) and when it was intra‐osseous, it occurred more frequently in the posterior mandible (mean age:14.33 ± 15.62 years). MFT occurred mainly in the mandible and was predominantly described as well‐circumscribed masses of spindle cells organized in fascicles with a prominent vascular activity in a hemangiopericytoma‐like pattern. The lesions were mainly positive for smooth muscle actin and vimentin immunomarkers. Surgical excision was the treatment of choice in the majority of cases and recurrence was observed in only three cases. Conclusion: MF and MFT affect more men, with an indolent clinical course. Intra‐osseous tumors and MFT seem to occur more frequently in younger individuals. These lesions seem to have a good prognosis and low recurrence. [ABSTRACT FROM AUTHOR]

This systematic review aimed to incorporate published information about synchronous odontogenic tumors (SOTs) with an analysis of the demographic and clinical characteristics from the cases published in the literature. Case reports and case series of SOT were searched in PubMed, Web of Science, Scopus, and EMBASE. A descriptive statistical analysis was performed. Twenty‐eight studies comprising 30 cases of SOTs were included. Considering all cases published, SOTs mostly occurred simultaneously in the maxilla and mandible (n = 19/63.3%). Lesions were bifocal in 13 (43.3% of all the 30 cases) and multifocal in 17 cases (56.7% of all the 30 cases). All SOTs available in the literature presented the same type of lesion, and two of them also involved another different SOT (n = 2/6.7% of all the 30 cases). Out of all published cases, the most frequent SOTs in the literature were odontomas (n = 10/33.3% of all the 30 cases), squamous odontogenic tumors (OTs) (n = 8/26.7% of all the 30 cases), calcifying epithelial OTs (n = 8/26.7% of all the 30 cases), and adenomatoid OTs (n = 2/6.7% of all the 30 cases). Considering all SOTs cases included, the overall recurrence was 13.3%. Inside a subgroup of the lesion, synchronous calcifying epithelial OT presented the highest (25%). Five cases (16.7% of all the 30 cases) had a previously associated syndrome, with two cases of Schimmelpenning syndrome being reported. Among published SOTs, odontomas were the most common. All SOTs available in the scientific literature showed the same type of OT and mainly affected both jaws simultaneously. Only a few of these cases were associated with a syndrome. [ABSTRACT FROM AUTHOR]

Background: Subgemmal neurogenous plaques (SNP) are composed of neural structures found in the posterolateral portion of the tongue, rarely biopsied as most of them are asymptomatic or eventually only clinically managed. We aimed to investigate a case series of possible correlation of symptomatic subgemmal neurogenous plaque (SNP) with coronavirus disease 2019 (COVID‐19). Methods: Eleven formalin‐fixed paraffin‐embedded cases from patients with previous confirmed COVID‐19 (by RT‐PCR) were retrieved from two pathology files. Histological sections were morphologically studied, and then submitted to immunohistochemical reactions against S‐100 and neurofilament proteins, neuron‐specific enolase, Glial fibrillary acidic protein (GFAP), synaptophysin, CD56, Ki67, cytokeratins (7, 8–18, 19, 20), nucleocapsid and spike proteins (SARS‐CoV‐1; and ‐2) and epithelial membrane antigen (EMA) antibodies. Clinical data were retrieved from the patients' medical files, including the symptoms and the complete history of the progression of the disease. Results: The patients who had COVID‐19 included in this study experienced painful lesions in the tongue that corresponded to prominent or altered SNP. Microscopically, neural structures were positive for S‐100, GFAP and neurofilament protein. And the cellular proliferative index (by Ki‐67) was very low. Conclusion: Thus, based on the current results, we hypothesize that symptomatic SNP may be a late manifestation of COVID‐19 infection. [ABSTRACT FROM AUTHOR]

Background: Primordial odontogenic tumour is a benign mixed neoplasm of recent description, which has histological similarities with other odontogenic tumours such as the ameloblastic fibroma. In this article, we investigate the architecture of the sub‐epithelial layer of mesenchymal cells expressing the marker CD34 in primordial odontogenic tumour. Objective: Analyse the spatial patterns of CD34 expression in primordial odontogenic tumour and compare them with those in ameloblastic fibroma and the normal tooth germ by means of objective imaging approaches, to better characterise these lesions. Methods: Two cases of primordial odontogenic tumour, four cases of ameloblastic fibroma and two cases of tooth germ in cap and bell stages were used for morphological, structural and immunohistochemical analyses. Results: CD34 expression was found in vascular endothelium of primordial odontogenic tumour, ameloblastic fibroma and tooth germ. In addition, a characteristic sub‐epithelial expression was observed only in primordial odontogenic tumour, corresponding to 84%–86% of the sample boundaries. Moreover, the zone expressing CD34 corresponded with a higher cellularity, which was absent in ameloblastic fibroma and tooth germ. Conclusion: Image analysis of the primordial odontogenic tumour architecture revealed characteristics absent in other odontogenic tumours and tooth germs. This study provides additional information to support the idea that this neoplasm is a distinct entity from early stage AF or developing odontoma. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to present and discuss the salient clinicopathological features, differential diagnosis and epithelial immunohistochemical profile of three additional cases of peripheral odontogenic keratocyst (POKC) and to present a review of the literature. POKC is a locally aggressive odontogenic lesion. The peripheral variant of the odontogenic keratocyst is rare and more frequently located in anterior gingiva. Material and Methods: We present the clinicopathological features of 3 new cases of POKC (2 women and 1 man; age range: 14–74 years). Immunohistochemical study included CK7, CK14, CK19 and Ki‐67, and a systematic review of the literature was performed in PubMed, Scopus and Web of Science databases. Results: All cases were located in the anterior gingiva (2 in maxilla and 1 mandible), and none corresponded to Gorlin–Goltz syndrome. High expression of CK14 was seen in all cases, with CK19 and CK7 been only focally positive. The expression of Ki‐67 was located in the basal and parabasal cells in all cases. Conclusions: POKC is a rare gingival lesion that seems to originate from remnants of dental lamina or from the basal cells of the gingival epithelium and present a similar histopathology as compared to intraosseous OKC. [ABSTRACT FROM AUTHOR]

Background: Hybrid odontogenic lesions combine histopathological characteristics of two or more odontogenic cysts and/or tumours. The aim of this study was to evaluate the available data on hybrid odontogenic lesions (HOL) and to analyse their epidemiological/clinical features and biological behaviour. Methods: An electronic search was done in January 2021 using multiple databases. Eligibility criteria encompassed publications with sufficient clinical and histological information to confirm the tumours' diagnoses. Results: A total of 147 articles were included in this study, comprising 203 cases. Calcifying odontogenic cyst associated with odontoma (COC/OD) (37/18.2%) was the most common HOL. Females were more affected with a mean age of 24.9 years. Lesions presented as asymptomatic swellings, with a mean evolution time of 8.2 months (0.3–96), and mean tumour size of 4.8 cm (0.3–7). Radiographic aspects frequently showed radiolucent (139/68.4%) and unilocular (52/25.6%) images with well‐defined limits (48/23.6%). The lesions mostly affected mandibular pre‐molars (69/34%) and mandibular molars (69/34%) regions. Enucleation (89/43.8%) and surgical excision (59/29%) were the most common treatment modalities. The mean follow‐up time was 33.8 months (0.5–216 months) and recurrences were observed in four cases (1.9%), all of which were central odontogenic fibroma associated with central giant cell granuloma (COF/CGCG). Conclusion: COC/OD is the most common HOL and recurrence is a rare event, being usually associated with the diagnosis of COF/CGCG. [ABSTRACT FROM AUTHOR]

Background: Brown tumors are giant cell-rich lesions that result from abnormal bone metabolism in hyperparathyroidism, one of the most common endocrine disorders worldwide. Brown tumors occasionally affect the jaws and, despite well-known clinical and microscopic features, their molecular pathogenesis remains unclear. We investigated the presence of pathogenic activating mutations in TRPV4, FGFR1, and KRAS in a cohort of brown tumors since these have recently been reported in giant-cell lesions of the jaws and non-ossifying fibromas of the bones (FGFR1 and KRAS), which are histologic mimics of brown tumors.Methods: We target sequenced 13 brown tumors of the jaws associated with primary or secondary hyperparathyroidism. As mutations in these genes are known to activate the MAPK/ERK signaling pathway, we also assessed the immunostaining of the phosphorylated form of ERK1/2 (pERK1/2) in these lesions.Results: KRAS pathogenic mutations were detected in seven cases (p.G12V n = 4, p.G12D n = 1, p.G13D n = 1, p.A146T n = 1). KRAS variants of unknown significance (VUS), p.A134T and p.E37K, were also detected. All samples showed wild-type sequences for FGFR1 and TRPV4 genes. The activation of the MAPK/ERK signaling pathway was demonstrated by pERK1/2 immunohistochemical positivity of the brown tumors´ mononuclear cells.Conclusion: Mutations in KRAS and activation of the MAPK/ERK signaling pathway were detected in brown tumors of hyperparathyroidism of the jaws, expanding the spectrum of giant cell lesions whose molecular pathogenesis involve RAS signaling. [ABSTRACT FROM AUTHOR]

Background: Juvenile spongiotic gingival hyperplasia (JSGH) is a distinct clinicopathological entity of the buccal gingiva of young patients which has been related to several factors such as plaque formation, hormonal modifications, and viral infections; however, its true etiopathogenesis remains unsolved. Several immunohistochemical studies have demonstrated the similarity between the junctional epithelium (JE) and the hyperplasic epithelium of JSGH. The objective of this study is to analyze the clinicopathological and immunohistochemical characteristics of JSGH to explain its origin.Methods: Clinicopathlogical data of 10 cases of JSGH (five men and five women) with a mean age of 13 years (range: 9 to 17 years) were collected. CK7, CK14, CK19, CD3, CD20, S100, and Ki-67 antibodies were used for comparative immunohistochemical study.Results: All the lesions showed hyperplasic epithelium in its central portion, exhibiting marked spongiosis, vascular proliferation, and a chronic inflammatory infiltrate on the subepithelial connective tissue. CK19 was positive in the whole hyperplasic epithelium of JSGH and the basal layer of the marginal gingiva, while expression of CK14 was present in all epithelial layers of both the JSGH and that of the marginal gingiva. The subepithelial inflammatory infiltrate has a larger amount of CD20 positive cells.Conclusion: JSGH is a reactive tumor of the gingiva that may have an odontogenic etiology, whose origin seems to be the remnants of JE. [ABSTRACT FROM AUTHOR]

Background: Langerhans cell histiocytosis (LCH) is a rare disorder characterized by abnormal proliferation and infiltration of histiocytic cells. Methods: This review focused on the main aspects associated with LCH. Results: LCH can involve single or multiple organs and systems, with bone and skin being the most commonly affected sites. Regarding skeletal manifestations, the jawbones are involved in about 20%–30% of all cases. Such lesions may present as unilocular or multilocular images mainly affecting the posterior mandible. Oral soft tissue lesions may also occur, with the gingiva and hard palate being the most frequently affected sites. Conclusion: The diagnosis and management of LCH are challenging, requiring a multidisciplinary approach, with dentists playing a central role since oral manifestations can be the first sign of the condition. [ABSTRACT FROM AUTHOR]

Objectives: The establishment of animal models of xenotransplantation can contribute to the elucidation of the molecular pathogenesis of ameloblastic fibrodentinomas (AFD) and it also provides an opportunity for drug tests. We aimed to evaluate the possibility of AFD tumour growth in a patient‐derived xenograft (PDX) model. In addition, we characterized the human tumour and the PDXs. Materials and Methods: A sample of a recurrent AFD was obtained and two fragments were contralaterally implanted subcutaneously in an 8‐week old female NUDE mouse. After 250 days, the PDXs were removed and submitted to histopathological and molecular analysis. Immunohistochemical reactions for Ki67 and the phosphorylated form of ERK1/2 were carried out in both, PDXs and human tumour, and the presence of BRAFV600E was assessed. Results: From day 135 onwards, the PDXs presented a growth peak and remained stable until day 250. Histopathologically, the PDXs presented the same features of the patient's tumour. Tumour cells exhibited Ki67 and pERK1/2 immunoexpression in the patient's tumour and PDX. The AFD was wild‐type for BRAFV600E. Conclusion: The PDX model recapitulated well the human tumour after a long implantation time, representing a possible model to study the AFD and other odontogenic tumours pathobiology. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to assess the frequency of KRAS mutation and its association with the presence of the MAPK/ERK signaling pathway proteins in adenomatoid odontogenic tumors. Study Design: Paraffin‐embedded tissue samples from nine cases of adenomatoid odontogenic tumor were used. Genomic DNA was extracted from each sample; in one case, genetic mutations in 50 cancer‐associated genes were examined by next‐generation sequencing. Hotspot mutations in the RAS family were analyzed by Luminex assay using the remaining eight cases. Subsequently, immunohistochemistry for KRAS, CRAF, BRAF, EGFR, ERK, MEK, and BRAFV600E was performed. Results: A KRAS G12D missense mutation was detected in the DNA sequence of the tumor cells, but it was not detected in the stromal tissue. KRAS G12V and KRAS G12R mutations were detected in two and four cases, respectively. For immunohistochemistry, all the cases were EGFR, KRAS, BRAF, CRAF positive, one case was ERK negative,and one case was MEK and ERK negative, all the other remaining cases were MEK and ERK positive. Conclusion: KRAS mutation at codon 12 and the presence of MAPK/ERK pathway proteins were detected suggesting their association with tumorigenesis of adenomatoid odontogenic tumors. [ABSTRACT FROM AUTHOR]

Objective: To immunohistochemically characterize a group of oral myofibroblastic lesions (MLs) and to evaluate the ultrastructural features of myofibroblasts. Material and Methods: Using a tissue microarray technique (TMA), cases of myofibroma (MF), of nodular fasciitis (NF), of desmoplastic fibroma (DF), and of myofibroblastic sarcoma (MS) from the Universidad Autónoma Metropolitana Xochimilco, and a Private Oral Pathology Service in Mexico City were stained with antibodies against alpha‐smooth muscle actin (α‐SMA), H‐caldesmon, vimentin, desmin, β‐catenin, CD34, anaplastic lymphoma protein kinase (ALK‐1), and Ki‐67. Results: Nineteen of the 22 MF cases, 2/5 of the NF cases, 1/10 of the DF cases, and 1/2 of the MS cases were positive for α‐SMA. 1/2 of the MS cases were positive for desmin; 6/10 of the DF cases were positive for β‐catenin, and 2 of the MF cases were positive for ALK‐1. All of the MLs were positive for vimentin and negative for H‐caldesmon and CD‐34. The Ki‐67 labeling index in all of the 8/22 MF, 3/5 NF, and 2/2 MS cases was ≥10%. For all of the MLs evaluated, ultrastructural analysis revealed spindle‐shaped cells containing endoplasmic reticulum and peripheral actin filament bundles. Conclusion: In certain myofibroblastic lesions, the use of auxiliary techniques (such as immunohistochemistry) can be critical for differential diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Primordial odontogenic tumour (POT) is a rare benign mixed epithelial and mesenchymal odontogenic tumour. POT is composed of dental papilla‐like tissue covered with cuboidal to columnar epithelium that resembles to inner and outer enamel epithelium of the enamel organ without dental hard tissue formation. The aim of this study was to examine pathogenesis of POT based on tumourigenesis and odontogenesis. Subjects and methods: Six cases of POT were submitted for study. DNA analysis and transcriptome analysis were performed by next‐generation sequencing. Expression of amelogenin, ameloblastin and dentin sialophosphoprotein (DSPP) was examined by immunohistochemistry. Results: There were no gene mutations detected in any of analysed 151 cancer‐ and 42 odontogenesis‐associated genes. Enamel protein‐coding genes of Amelx, Ambn and Enam, and dentin protein‐coding genes of Col1a1, Dspp, Nes and Dmp1 were expressed, whereas expression of dentinogenesis‐associated genes of Bglap, Ibsp and Nfic was negative or very weak suggesting inhibition of dentin formation in POT after odontoblast differentiation. Immunoreactivity of amelogenin, ameloblastin and DSPP was detected in POT. Conclusions: Pathogenesis of POT is considered to be genetically different from other odontogenic tumours. It is suggested that inhibition of enamel and dentin formation in POT is due to defects in dentin formation process. [ABSTRACT FROM AUTHOR]

Focal acantholytic dyskeratosis (FAD) is a rare mucocutaneous disorder, first described by Helwig in 19571 as an "isolated form of Darier disease." We believe that tobacco might have acted as a chronic irritative agent in the establishment and clinical appearance of our patient's lesions (Table 1), and although FAD is not an oral premalignant disorder, lesions should be treated and patients must remain under periodical control. The clinical differential diagnosis of oral multifocal FAD includes proliferative multifocal leukoplakia, oral lichenoid disease, and pyostomatitis vegetans,3,4 however, rarity of FAD usually delays the diagnosis. [Extracted from the article]

Abstract: Background: Connective tissue autoimmune diseases (CTADs) constitute a group of conditions, including rheumatoid arthritis; systemic lupus erythematosus; mixed connective tissue disease; calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia (CREST) syndrome; scleroderma; dermatomyositis; and Sjögren syndrome. There are few studies on the alterations in filiform papillae in CTAD. Thus, the objective of this work was to determine whether there are changes in the macroscopic and dermoscopic patterns of filiform papillae. Methods: This case–control study included patients who were diagnosed with CTAD. The dependent variable was the dermoscopic pattern of filiform papillae of the tongue, and the independent variables were age, gender, time of evolution, and current treatment. A photograph of the back of the tongue was taken, and subsequently, the same site was examined by dermatoscopy. The microscopic and dermoscopic patterns of filiform papillae were classified (Maeda). Results: We included 50 cases and 50 controls, 94% of whom were female. The mean age was 43.96 ± 14.65 years. Of the cases with CTAD, 25% presented with a normal macroscopic pattern, versus 36% (18) with pattern II, 12% (6) with pattern III, and 20% (10) with pattern IV. The dermoscopic pattern was type I in 23 cases (46%), type II in 16 (32%), type III in 10 (20%), and type IV in one patient (2%). Conclusions: We have noted alterations in filiform papillae in CTADs, which emphasizes the importance of a detailed intraoral exploration and the macroscopic and dermoscopic evaluation of the dorsum of the tongue, specifically the filiform papillae. [ABSTRACT FROM AUTHOR]

Primordial odontogenic tumor (POT) is composed of variably cellular myxoid connective tissue, surrounded by cuboidal to columnar odontogenic epithelium resembling the inner epithelium of the enamel organ, which often invaginates into the underlying connective tissue. The tumor is delimited at least partially by a thin fibrous capsule. It derives from the early stages of tooth development. Syndecan‐1 is a heparan sulfate proteoglycan that has a physiological role in several cellular functions, including maintenance of the epithelial architecture, cell‐to‐cell adhesion and interaction of cells with extracellular matrix, and with diverse growth factors, stimulating cell proliferation. Ki‐67 is considered the gold standard as a cell proliferation marker. The aim of this study was to examine the expression of Syndecan‐1 and Ki‐67 proliferation index in POT and normal tooth germs to better understand the biological behavior of this tumor. Results showed that Syndecan‐1 was more intensely expressed in subepithelial mesenchymal areas of POT, in a pattern that resembles the early stages of tooth development. The cell proliferation index (4.1%) suggests that POT is a slow growing tumor. Syndecan‐1 expression in tooth germs in late cap and early bell stages was similar to POT, showing immunopositivity in subepithelial mesenchymal condensed areas. The immunohistochemical findings showed a pattern in which the population of subepithelial mesenchymal cells exhibited greater proliferative activity than the central portion of the dental papilla. [ABSTRACT FROM AUTHOR]

Primordial odontogenic tumor (POT) is a benign mixed epithelial and mesenchymal odontogenic tumor included into the current World Health Organization (WHO) classification of Head and Neck tumours in 2017. As far as the authors have confirmed, only eight cases of this tumor have been reported so far. This paper reports a case of POT that occurred in the right mandible of a 5-year-old patient. Panoramic radiograph showed a well-defined homogeneous radiolucency displacing the unerupted second deciduous molar to the deep part of the mandible. Histopathologically, the tumor was composed of cell-rich mesenchymal tissue with myxoid areas, surrounded by columnar epithelium and non-keratinized cuboidal epithelium in the outer layers. The histopathological diagnosis was POT. The expression patterns of cytokeratins (CK) 14, 18, 19, vimentin and CD34 suggested that the grade of differentiation of the POT was approximately equivalent to that of normal primary tooth germ tissues in cap stage to late bell stage. [ABSTRACT FROM AUTHOR]

Background: Ameloblastoma is a benign but locally aggressive odontogenic tumor, while ameloblastic carcinoma is its malignant counterpart. Angiogenesis and lymphangiogenesis in malignancies have been correlated with higher aggressiveness and poor prognosis, as well as greater expression of podoplanin by tumoral cells.Methods: Immunohistochemical expression of podoplanin, CD34, and CD105 (endoglin) was evaluated in 53 ameloblastomas and three ameloblastic carcinomas; additionally, immunohistochemistry for podoplanin was also performed in 10 tooth germs. Microvessel density of blood and lymphatic vessels was calculated and compared between ameloblastomas and ameloblastic carcinomas. Immunoexpression of podoplanin by ameloblastic cells was evaluated in tooth germs, ameloblastomas, and ameloblastic carcinomas.Results: Podoplanin was similarly expressed by odontogenic epithelial cells of tooth germs and ameloblastomas, while its expression was lower in ameloblastic carcinomas. There was no difference in microvessel density assessed by CD34 between ameloblastomas and ameloblastic carcinomas; nevertheless, the latter presented higher amounts of lymphatic and new formed blood vessels.Conclusions: Results suggest that podoplanin does not seem to be involved in invasion mechanisms of ameloblastic carcinomas, as its expression was decreased in the malignant tumoral cells. On the other hand, the increased lymphatic microvessel density and neoangiogenesis found in ameloblastic carcinomas could be related to its aggressiveness and potential for metastasis. [ABSTRACT FROM AUTHOR]

Background: Cyclooxygenase-2 (COX-2) catalyses the conversion of arachidonic acid to prostaglandin, and its overexpression has been demonstrated in different malignant tumors, including cutaneous melanoma. However, no data about the expression of this protein in oral melanocytic lesions are available to date. The aim of this study was to evaluate the immunohistochemical expression of COX-2 in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions.Methods: COX-2 was evaluated by immunohistochemistry in 49 oral melanocytic lesions, including 36 intramucosal nevi and 13 primary oral melanomas, and in four cutaneous nevi and eight melanomas.Results: All cases of oral and cutaneous melanomas were positive for COX-2. On the other hand, all oral and cutaneous melanocytic nevi were negative.Conclusion: COX-2 is highly positive in oral melanomas and negative in oral nevi and might represent a useful marker to distinguish melanocytic lesions of the oral cavity. [ABSTRACT FROM AUTHOR]

Aim To describe the clinicopathological and immuno-histochemical features of six tumours that do not fulfil the criteria of any of the currently classified odontogenic tumours. Methods and results The patients were three males and three females, whose ages ranged from 3 years to 18 years (mean, 11.05 years). In all cases there were well-defined radiolucencies associated with unerupted teeth apparently showing a pericoronal relationship. Microscopically, all tumours were composed of variably cellular loose fibrous tissue with areas similar to dental papilla, entirely surrounded by cuboidal to columnar epithelium resembling the internal epithelium of the enamel organ. Mesenchymal tissue was positive only for vimentin, and Ki67 expression was very low (<2%). The epithelium was positive for CK AE1/ AE3, CK5, CK14, and CK19, but negative for CK18 and CK20. All cases showed clear demarcation from the surrounding bone, and were surgically removed, with no recurrences after follow-up ranging from 6 months to 20 years. Conclusions These findings differ from those observed in other odontogenic lesions, such as ameloblastic fibroma, odontogenic myxoma, odontogenic fibroma, and hyperplastic dental follicles. The term primordial odontogenic tumour is proposed to describe this novel lesion. [ABSTRACT FROM AUTHOR]

SARS-CoV-2, severe acute respiratory syndrome coronavirus 2 gl Previous studies reported that the levels of ACE2 messenger RNA expression in oral mucosa and minor SGs was similar or even higher than levels observed in the lungs.6,7 In fact, in 2011, Liu et al.8 showed that epithelial cells of the SG ducts of Rhesus monkey express ACE2 and are therefore early targets for SARS-CoV infection. In summary, the high immunohistochemistry expression of ACE2 found in vessels and ductal structures indicate that intraoral SGs may be involved in SARS-CoV-2 infection, and consequently, as described previously, may act as viral reservoir. Keywords: ACE2 enzyme; COVID-19; respiratory viruses; SARS-CoV-2 EN ACE2 enzyme COVID-19 respiratory viruses SARS-CoV-2 1905 1906 2 02/19/21 20210401 NES 210401 Angiotensin-converting enzyme 2 (ACE2) plays a pivotal role in the regulation of blood pressure, and it is the main cell receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19).1,2 It has been reported that increased expression of ACE2 favors the development of the aggressive form of COVID-19.3 Some symptoms of COVID-19 including anosmia and ageusia occur probably due to infection of the cells of the respiratory and oral mucosa by SARS-CoV-2, respectively. [Extracted from the article]

Three cases of cartilaginous choristomas of the tongue are presented. Two lesions occurred in women of 71 and 28 years of age whose lesions were located in the middle third of the dorsum. The other lesion was found on the left lateral border in a 27-year-old man. The clinical, microscopic and immunohistochemical features are described. The lesions were easily excised with no recurrence after follow-up periods of at least 6 months. The histogenesis and the differential diagnosis are discussed, and the literature is reviewed. [ABSTRACT FROM AUTHOR]

Angiocentric lymphomas (AL) involving the mid-face are infrequent lesions. Their incidence seems to be higher in certain Asian and Latin American countries, where most of the reported series reveal a predominance of T-cell lineage and a high frequency of EBV-positive cells. The clinical and pathological features of 12 AL that affected the palate are presented. Immunophenotypic studies were performed in nine of these cases. Seven (77%) demonstrated T-cell lineage, one was of B-cell origin and one could not be classified. The high incidence of T-cell lesions in this and other studies supports the existence of geographical and possibly of etiological differences in these neoplasms. [ABSTRACT FROM AUTHOR]

Objective The aim of this study was to show the epidemiological features of 25 malignant odontogenic tumors ( MOT) in Latin America. Materials and Methods We retrieved 25 cases of MOT out of 2142 odontogenic tumors, from four oral diagnostic centers in Latin America, and described the main clinical and pathological characteristics. Results A total of 19 cases were carcinomas, including eight ameloblastic carcinomas, five primary intra-osseous squamous cell carcinomas, three clear cell odontogenic carcinomas and three ghost cell odontogenic carcinomas. All six sarcomas corresponded to ameloblastic fibrosarcoma. Thirteen cases occurred in men and 12 in women, age ranged from 7 to 77 years old, with a mean of 41.4 years. The average age of patients with carcinomas and sarcomas were 48.53 and 19 years old, respectively. Conclusion As malignant odontogenic tumors are very rare, this series helps to better clarify their relative frequency, predominant subtypes, and clinical characteristics in Latin America. [ABSTRACT FROM AUTHOR]

Aims Signet-ring cell ( SRC) change has not been reported in adenoid cystic carcinoma ( ACC). The aim of this study was to describe the clinicopathological and immunohistochemical findings in four cases of ACC with SRCs ( ACC- SRC), in which the relative proportion of the SRC component ranged from 25% to 50%. Methods and results The median age was 58 years (range: 48-81 years), and all patients were women. The involved sites were sinonasal, lip, and submandibular. Two patients developed lung metastasis, and one died of disease 63 months after tumour resection. Neither mucinous nor lipid substances were detected in the SRCs. These showed positive staining for AE1/ AE3, cytokeratin 14, and epithelial membrane antigen, which highlighted the intracytoplasmic vacuole borders. The SRC nests were surrounded by myoepithelial cells positive for α-smooth muscle actin and p63. The SRCs showed similar p53 positivity but lower Ki67 and mitotic indices than the conventional component. SRCs were c-Myb-negative. Ultrastructural examination revealed that the intracytoplasmic vacuoles were lumina lined by microvilli. Conclusions ACC- SRC is a non-mucin-producing and non-lipid-producing phenomenon, possibly related to disturbed differentiation of ductal/luminal cells. This cellular modification in ACC apparently does not change the biological behaviour of the tumour, but it may cause significant diagnostic problems, particularly in incisional biopsies. [ABSTRACT FROM AUTHOR]

Oral Diseases (2011) 17, 808-812 Objective: The aim of this study was to determine the expression of fatty acid synthase (FASN) in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions. Materials and Methods: Expression of FASN was evaluated by immunohistochemistry in 51 oral melanocytic lesions, including 38 intramucosal nevi and 13 primary oral melanomas, in 10 cutaneous nevi and in 14 melanomas. Results: Fatty acid synthase was strongly expressed only in melanomas, either of the oral mucosa or cutaneous. On the other hand, most oral and cutaneous nevi were negative, with a few oral cases showing focal and weak expression. Conclusion: Fatty acid synthase is expressed in malignant melanocytes, and it can be a helpful marker to distinguish oral melanomas from oral melanocytic nevi. [ABSTRACT FROM AUTHOR]

The aims of the present study were to examine whether the pattern of syndecan-1 expression correlates with cellular proliferation index in desmoplastic ameloblastomas (DA), peripheral ameloblastomas (PA) and ameloblastic carcinomas (AC), and to compare with that previously reported for solid (SA) and unicystic (UA) variants of ameloblastoma. Immunohistochemistry was performed for syndecan-1 and Ki-67 in seven ameloblastomas (four DA and three PA) and three AC. Expression of syndecan-1 was related to the histological subtype of tumors and, in the case of malignancy, to lower expression levels observed in AC (22.5%) than in PA (47.5%) or DA (77.5%) ( P < 0.05). Syndecan-1 expression correlated inversely with Ki-67 proliferative index: the expression was lower in both types of ameloblastomas (1.5% in DA and 6.4% in PA) than in AC (41.2%; P < 0.05). The present results suggest that the decrease in syndecan-1 expression and increase in the Ki-67 index observed in AC is in accordance with its higher aggressiveness as compared to the rare DA and PA. Interestingly, DA had a lower proliferation index as well as the highest levels of syndecan-1 expression. These data suggest that DA differ from the other types of intraosseous ameloblastomas but more studies are necessary to better understand the role of this protein as a marker in the biological behavior of the epithelial odontogenic neoplasms. [ABSTRACT FROM AUTHOR]

This article describes a case of clear cell odontogenic carcinoma (CCOC) in a 55-year-old woman who presented such a tumor extending from the midline of the mandible to the right first molar. The tumor was surgically excised and has not recurred or metastasized 6 months after surgery. To date, only 33 well-documented cases have been reported (including the present case) in the English literature. Twenty-eight (84.8%) have developed in the mandible and five (15.2%) in the maxilla. Eighteen (54.5%) occurred anterior to the first molar. The vast majority have been diagnosed in patients older than 40 years (30/33), and the mean age at diagnosis is 57.4 years (range: 17-89), with a male/female ratio: 1/2. Recurrences have been described in 17 cases (51.5%) and metastasis in 10 (30.3%). Based on its morphologic, histochemical and immunophenotypic features, CCOC should be distinguished from other primary and metastatic clear cell tumors of the oral and maxillofacial regions. [ABSTRACT FROM AUTHOR]

Background: Calcifying odontogenic cyst was described first by Gorlin et al. in 1962; since then several hundreds of cases had been reported. In 1981, Prætorius et al. proposed a widely used classification. Afterwards, several authors proposed different classifications and discussed its neoplastic potential. The 2005 WHO Classification of Odontogenic Tumours re-named this entity as calcifying cystic odontogenic tumour (CCOT) and defined the clinico-pathological features of the ghost cell odontogenic tumours, the CCOT, the dentinogenic ghost cell tumour (DGCT) and the ghost cell odontogenic carcinoma (GCOC). Methods: The aim of this paper was to review the clinical-pathological features of 122 CCOT, DGCT and GCOC cases retrieved from the files of the oral pathology laboratories from 14 institutions in Mexico, South Africa, Denmark, the USA, Brazil, Guatemala and Peru. It attempts to clarify and to group the clinico-pathological features of the analysed cases and to propose an objective, comprehensive and useful classification under the 2005 WHO classification guidelines. Results: CCOT cases were divided into four sub-types: (i) simple cystic; (ii) odontoma associated; (iii) ameloblastomatous proliferating; and (iv) CCOT associated with benign odontogenic tumours other than odontomas. DGCT was separated into a central aggressive DGCT and a peripheral non-aggressive counterpart. For GCOC, three variants were identified. The first reported cases of a recurrent peripheral CCOT and a multiple synchronous, CCOT are included. Conclusions: Our results suggest that ghost cell odontogenic tumours comprise a heterogeneous group of neoplasms which need further studies to define more precisely their biological behaviour. [ABSTRACT FROM AUTHOR]

Aim: To classify 163 ameloblastoma cases according to the new WHO Classification of Odontogenic Tumours (2005) and analyse their clinical and microscopic features. Methods: We studied the clinico-pathological features of 163 ameloblastoma cases from nine regional Latin-American institutions from Mexico and Guatemala. Results: Ameloblastomas comprised 22.7% of all odontogenic tumours. The mean age was 41.4 years for solid ameloblastoma (SA) and 26.3 years for unicystic ameloblastoma (UA) ( P < 0.001) and both sexes were almost equally affected. The mandible was mainly affected for both UA and SA. The mean size was 6.2 cm for SA and 6.3 cm for UA cases. The recurrence rate was 21.7% for SA and 12.6% for UA. UA was twice as more frequent than the solid variant. Conclusions: In this study we found that UA was frequently misdiagnosed as SA; however, there are enough clinical and microscopic features that allow for an accurate differentiation between both types of ameloblastoma that should be recognized for surgical and prognostic purposes. In this study, SA was not found in patients younger than 20 years, UA had a constant myxoid stroma while mature connective tissue was more frequently associated with the solid type. [ABSTRACT FROM AUTHOR]

The lesion is associated with a retained tooth, which is included within the tumour mass or displaced by it. GLO:EW1/01feb20:his13999-fig-0002.jpg PHOTO (COLOR): Histopathological features: primordial odontogenic tumour is entirely surrounded by cuboidal to columnar epithelium that resembles the internal epithelium of the enamel organ (A). Histologically, the tumour recalls the primary stages of tooth development where neither dentin nor enamel are produced. [Extracted from the article]

We report two cases of an uncommon odontogenic lesion, previously described as adenomatoid dentinoma. They were well-circumscribed unilocular radiolucent lesions exhibiting discrete radiopacities, located in the left mandibular third molar region. Microscopically they were composed of odontogenic hard and soft tissues, similar to a dental germ. Dental papilla and dentin were easily identified. Odontogenic epithelium formed adenomatoid-like structures, and by scanning electron microscopy a layer of enamel was seen in contact with the dentin. Based on these clinical, radiographic, histological and electron microscopical features we proposed the diagnosis of adenomatoid odontogenic hamartoma. Treatment consisted of surgical removal, and no recurrence was observed. In our opinion all similar cases previously reported pertain to the same spectrum of this lesion and thus should be named as suggested above. Moreover, ultrastructural observations using 5 μm sections can be useful to better characterize the presence of hard tissues. [ABSTRACT FROM AUTHOR]

Examines the clinical features of congenital generalized hypertrichosis with gingival hyperplasia. Etiology of the disease; Variations in the diagnosis of the disease; Therapeutic approaches.

A case of leiomyomatous hamartoma located on the anterior third of the tongue in an otherwise healthy 6-year-old boy is reported. The lesion had been present since birth as an asymptomatic, pedunculated tubular tumour. The lesion was surgically excised and histopathological examination disclosed a non-neoplastic mass composed of irregularly arranged bundles of smooth muscle embedded in a fibrovascular stroma. No recurrence was observed after 1 year of follow-up. [ABSTRACT FROM AUTHOR]

A response from the authors of the article regarding an understanding of the reported primordial odontogenic tumour (POT) in the 2015 Volume 66 issue is presented.

J Oral Pathol Med (2012) 41: 389-393 Although molecular alterations are reported in different types of odontogenic tumours, their pathogenesis remains to be established. Loss of heterozygosity (LOH) studies allow the identification of minimal regions of deletions of known or putative tumour suppressor genes, the losses of which may promote neoplastic growth. The purpose of this study was to investigate LOH in a set of odontogenic mixed tumours. Tumour suppressor gene loci on 3p, 9p, 11p, 11q and 17p chromosomes were analysed in five samples of ameloblastic fibroma (AF), three samples of ameloblastic fibro-odontoma (AFO) and three samples of ameloblastic fibrosarcoma (AFS). The most frequently lost genetic loci were p53 (17p13, 62%) and CHRNB1 (17p13, 55%). LOH at the chromosome regions 3p24.3, 9p22 and 9p22-p21 was identified only in AFS. No sample showed LOH at the chromosomal loci 3p21.2 and 11q13.4. For the region 9p22-p13, LOH occurred in one sample of AFO. The fractional allelic loss (FAL) was calculated for each sample. The mean FAL of the benign lesions (i.e. AF and AFO) was 22%, whereas the mean FAL of the malignant lesions (i.e. AFS) was 74.6%. In conclusion, our results show a higher FAL in AFS compared to its benign counterparts and reveal a different pattern of LOH of tumour suppressor genes in AFS, which may regulate changes in tumour behaviour. [ABSTRACT FROM AUTHOR]

Background: Cyclooxygenase-2 (COX-2) catalyses the conversion of arachidonic acid to prostaglandin, and its overexpression has been demonstrated in different malignant tumors, including cutaneous melanoma. However, no data about the expression of this protein in oral melanocytic lesions are available to date. The aim of this study was to evaluate the immunohistochemical expression of COX-2 in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions., Methods: COX-2 was evaluated by immunohistochemistry in 49 oral melanocytic lesions, including 36 intramucosal nevi and 13 primary oral melanomas, and in four cutaneous nevi and eight melanomas., Results: All cases of oral and cutaneous melanomas were positive for COX-2. On the other hand, all oral and cutaneous melanocytic nevi were negative., Conclusion: COX-2 is highly positive in oral melanomas and negative in oral nevi and might represent a useful marker to distinguish melanocytic lesions of the oral cavity., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)