Use of calretinin in the differential diagnosis of unicystic ameloblastomas

New perspectives in the differential diagnosis of jaw lesions: Machine learning and inflammatory biomarkers

This study aimed to assess the diagnostic performance of a machine learning approach that utilized radiomic features extracted from Cone Beam Computer Tomography (CBCT) images and inflammatory biomarkers for distinguishing between Dentigerous Cysts (DCs), Odontogenic Keratocysts (OKCs), and Unicystic Ameloblastomas (UAs). This retrospective study involves 103 patients who underwent jaw lesion surgery in the Maxillofacial Surgery Unit of Federico II University Of Naples between January 2018 and January 2023. Nonparametric Wilcoxon-Mann-Whitney and Kruskal Wallis tests were used for continuous variables. Linear and non-logistic regression models (LRM and NLRM) were employed, along with machine learning techniques such as decision tree (DT), k-nearest neighbor (KNN), and support vector machine (SVM), to predict the outcomes. When individual inflammatory biomarkers were considered alone, their ability to differentiate between OKCs, UAs, and DCs was below 50 % accuracy. However, a linear regression model combining four inflammatory biomarkers achieved an accuracy of 95 % and an AUC of 0.96. The accuracy of single radiomics predictors was lower than that of inflammatory biomarkers, with an AUC of 0.83. The Fine Tree model, utilizing NLR, SII, and one radiomic feature, achieved an accuracy of 94.3 % (AUC = 0.95) on the training and testing sets, and a validation set accuracy of 100 %. The Fine Tree model demonstrated the capability to discriminate between OKCs, UAs, and DCs. However, the LRM utilizing four inflammatory biomarkers proved to be the most effective algorithm for distinguishing between OKCs, UAs, and DCs.

Expression of Calretinin Expression in Odontogenic Cysts and Odontogenic Tumors - Original Research

Aim

The present study was conducted for assessing variability in calretinin expression among odontogenic cysts as well as tumor cases.

Materials and Methods

Fifteen cases were included in the present research consisting of cases like - dentigerous cyst, odontogenic keratocyst, apical radicular cyst along with tumors like ameloblastoma, ameloblastic carcinoma, adenomatoid odontogenic tumor. Calretinin antibody was used for immunohistochemical staining. The amount of expression of this calretinin was statistically analyzed with the help of Chi-square test where P < 0.05 was considered noteworthy statistically.

Results

Most cases of ameloblastomas were highly positive for calretinin expression as compared to other cysts and tumors. Therefore, the correlation of this variation of expression of calretinin was statistically noteworthy (P = 0.00).

Conclusion

In this study, we concluded that for ameloblastomas, calretinin can be a specific marker immunohistochemically and can help in identifying the amount of aggressive spread of various odontogenic tumors.

Adenoid 'ameloblastoma': Clinicopathological description of 4 additional BRAF-negative cases

OBJECTIVE

Adenoid ameloblastoma (AA) is an epithelial odontogenic tumor that was recognized as a separate entity in the last odontogenic classification of WHO in 2022. The etiology is unknown, and the pathogenesis remains controversial. The objective of this study is to contribute the clinicopathological features of 4 additional BRAF-negative cases to the existing literature, aiming to enhance the molecular understanding of this unique tumor in the forthcoming classification.

MATERIALS AND METHODS

This study consists of a case series of four patients diagnosed with AA. The patients' demographic and clinical information were collected from the universities' medical achieves. Histopathologically, all cases were reexamined according to the latest update of the WHO odontogenic tumor classification. In addition to H&E and immunohistochemical stains, cytogenetics was also evaluated.

RESULTS

Well-defined unilocular radiolucent lesions were observed in all cases. Ameloblastoma-like components exhibited reserved nuclear polarity, suprabasal stellate reticulum-like epithelium, duct-like structure, whorls/morules, and cribriform architecture were common features. Variable immunoreactivity to CK7, CK19, CK14, p63, and p40 were determined, and proliferative activity was greater than 15%. The BRAF molecular study revealed no mutations.

CONCLUSIONS

When diagnosing AA, the essential histopathological characteristics must be rigorously applied, and a significant portion of the lesion should contain these features. Additionally, despite limited molecular data, since the BRAF mutation commonly observed in ameloblastomas is not present in the majority of AA cases, we propose changing the term "ameloblastoma" to "ameloblastic" and referring to it as "adenoid ameloblastic tumor" in the forthcoming classification.

Immunohistochemical expression of Ki-67 and Glypican-3 to distinguish aggressive from nonaggressive benign odontogenic tumors

Background

The benign neoplasms are normally slow growing, indolent with no invasive potential. However, there exist a few locally aggressive benign odontogenic tumors that have a tendency to invade and deform the surrounding structures. The exact reason for the aggressiveness of these benign neoplasms remained an enigma. Their biology and clinical expression can often be destructive and ominous. An appropriate treatment protocol needs to be followed to combat the high recurrence rate and aggressiveness of these entities. Aggressive and noniaggressive epithelial odontogenic tumors were analyzed immunohistochemically with Ki-67 and glypican 3 (GPC3).

Materials and Methods

Fifty-nine cases of tumors were divided into aggressive odontogenic tumors (20 solid ameloblastomas, four unicystic ameloblastoma, and 28 keratocystic odontogenic tumors) and nonaggressive odontogenic tumors (five adenomatoid odontogenic tumors and two calcifying cystic odontogenic itumors).

Results

Statistical analysis using Pearson correlation showed Ki-67 to be a better marker for differentiating aggressive from nonaggressive odontogenic tumor as compared to GPC3 (P < 0.001, highly significant), whereas among aggressive tumors, GPC3 turned out to be more useful as compared to Ki-67 (P < 0.001, highly significant).

Conclusion

The present study provides an insight into the different biological behavior of odontogenic tumors, which can thus be helpful in determining the therapy strategies for more aggressive odontogenic tumors.

How "Neuronal" Are Human Skin Mast Cells?

Mast cells are evolutionarily old cells and the principal effectors in allergic responses and inflammation. They are seeded from the yolk sac during embryogenesis or are derived from hematopoietic progenitors and are therefore related to other leukocyte subsets, even though they form a separate clade in the hematopoietic system. Herein, we systematically bundle information from several recent high-throughput endeavors, especially those comparing MCs with other cell types, and combine such information with knowledge on the genes’ functions to reveal groups of neuronal markers specifically expressed by MCs. We focus on recent advances made regarding human tissue MCs, but also refer to studies in mice. In broad terms, genes hyper-expressed in MCs, but largely inactive in other myelocytes, can be classified into subcategories such as traffic/lysosomes (MLPH and RAB27B), the dopamine system (MAOB, DRD2, SLC6A3, and SLC18A2), Ca²⁺-related entities (CALB2), adhesion molecules (L1CAM and NTM) and, as an overall principle, the transcription factors and modulators of transcriptional activity (LMO4, PBX1, MEIS2, and EHMT2). Their function in MCs is generally unknown but may tentatively be deduced by comparison with other systems. MCs share functions with the nervous system, as they express typical neurotransmitters (histamine and serotonin) and a degranulation machinery that shares features with the neuronal apparatus at the synapse. Therefore, selective overlaps are plausible, and they further highlight the uniqueness of MCs within the myeloid system, as well as when compared with basophils. Apart from investigating their functional implications in MCs, a key question is whether their expression in the lineage is due to the specific reactivation of genes normally silenced in leukocytes or whether the genes are not switched off during mastocytic development from early progenitors.

Keratoameloblastoma: A Report of Seven New Cases and Review of Literature

BACKGROUND

Keratoameloblastoma (KA) is an uncommon and controversial variant of ameloblastoma exhibiting central keratinisation. Due to their rarity, there is limited information in the literature on their clinical, radiologic and histologic features. This study adds seven additional cases of KA to the literature, and reviews the current published literature on this rare entity.

METHODS

KAs were retrospectively reviewed over a 20-year period from three Oral and Maxillofacial Pathology Laboratories. Included cases were examined and the diagnosis confirmed under conventional microscopy. Immunohistochemistry with the use of a monoclonal antibody against calretinin was performed on included cases. The clinical, radiologic and histologic features of the seven new cases of KA were analysed and compared to existing cases in the literature.

RESULTS

KAs presented at a mean age of 40 years with a nearly equal gender distribution and a mandibular predilection (65%). The majority (92%) of cases presented with localised swelling with associated pain in 32% of cases. Mixed density or internal calcifications were noted in 40% of cases. All tumours presented with bony expansion, with cortical destruction noted in 62% of cases. Histologically, all tumours consisted of solid and cystic follicles with surface parakeratinisation and lamellated accumulations of central keratin. In areas the cystic follicles had an epithelial lining suggestive of an OKC. There were focal luminal areas of loosely arranged polygonal cells reminiscent of the stellate reticulum. The basal cells consisted of columnar cells with evidence of palisading and prominent subnuclear vacuolisation. Of the cases treated via tumour resection, 27% presented with tumour recurrence.

CONCLUSION

This case series reports seven additional cases of KA, taking the total to 26 reported cases. The identification of subtle histologic features, including focal stellate reticulum-like central areas, subnuclear vacuolisation and lamellated-type central keratinisation, are key in diagnosing KA. The radiologic features will often indicate signs of aggressiveness such as cortical destruction, differentiating KA from OKC. All cases were completely negative for calretinin IHC, limiting its use in distinguishing KA from OKC. Further large series are needed to expand the current understanding of this rare variant of ameloblastoma.

Mandibular unicystic ameloblastoma revealed by florid epulis of the gum: Case report

Ameloblastomas are quite frequent odontogenic tumors, they can be intraosseous or peripheral to the gum, it's rare to find an intraosseous ameloblastoma with gingival extension. Here, we report the case of a 40 years old woman who presented with an exophytic gingival lesion at the gum level of the 46 tooth that was extracted at a quack 01 years before her consultation due to pain in this area. Clinical and radiological examination revealed the presence of two tumors in the same area. The patient benefited from an excision of her gingival tumor and an enucleation of her intraosseous tumor. Histopathological and immunohistochemical examinations revealed that the respective tumors were a spindle cell epulis and an intraluminal unicystic ameloblastoma of different origins, leaving the question and search for the relationship between these two tumors. The postoperative course was uneventful during the 12-month follow-up period after surgical treatment.

Comparison of calretinin expression in dentigerous cysts and ameloblastoma: An immunohistochemical study

Background:

Calretinin is a calcium-binding protein of 29-kilodalton (kDa), which is widely expressed in normal human tissues and tumorigenic tissues. Its expression in the odontogenic epithelium during odontogenesis and in neoplastic odontogenic tissues has been demonstrated. Unicystic ameloblastoma poses a diagnostic challenge, as its histologic presentation can be sometimes mistaken for cystic odontogenic lesions. In the present study, an attempt is made to overcome the confusion encountered in the diagnosis of dentigerous cyst and unicystic ameloblastoma, using the expression of calretinin in both lesions and to compare this expression with conventional ameloblastoma to accurately diagnose and differentiate these lesions.

Materials and Methods:

A total of eighty cases, in which twenty cases each of ameloblastoma, unicystic ameloblastoma, dentigerous cyst, and odontogenic keratocyst (OKC) were included in the study. Slides were made from the archival blocks of each case and were stained immunohistochemically with calretinin.

Results:

Correlation between calretinin staining and histopathological diagnosis was done, and it was found that all twenty cases of ameloblastoma showed positivity for calretinin, whereas 17 of twenty cases of unicystic ameloblastoma showed positivity for calretinin staining. All the cases of OKC and dentigerous cyst were negative for calretinin.

Conclusion:

Calretinin may serve as an important diagnostic adjunct in the differential diagnosis of ameloblastoma and cystic odontogenic lesions.

Expression of calretinin in odontogenic keratocysts and basal cell carcinomas: A study of sporadic and Gorlin-Goltz syndrome-related cases

Gorlin-Goltz syndrome (GGS), is an autosomal dominant inherited disorder related to germline mutation of PTCH1 gene, characterised by the presence of multiple developmental anomalies and tumours, mainly basal cell carcinomas (BCC) and odontogenic keratocysts (OKC). We analysed and compared the expression of calretinin in 16 sporadic OKCs, from 15 patients, and 12 syndromic OKCs from 11 patients; in 19 BCC's and 2 cutaneous keratocysts (CKC) belonging to 4 GGS patients, 15 sporadic BCCs and 3 steatocystomas (SC). Calretinin was negative in 10 of 12 syndromic OKCs, focally positive (<5% of cells) in 2; six sporadic OKCs were negative, 6 focally and 4 diffusely positive (p = .02, cases focally and diffusely positive vs. cases negative). All BCCs of 3 GGS patients were negative, the fourth patient presented two BCCs negative and 5 focally or diffusely positive; 7 sporadic BCCs were negative and 8 focally positive (p = NS). Two CKCs resulted negative in one GGS patient; 2 sporadic SCs were positive, and a third was negative. PTCH1 mutations produce an altered PTCH protein and an aberrant activation of Sonic hedgehog (SHH) pathway, leading to tumoral proliferation. It has been demonstrated that treatment of human foetal radial glia cells with SHH reduces, whereas the blockage of SHH increases calretinin expression. We found a lower expression of calretinin in syndromic OKCs compared to sporadic cases. Although calretinin's value in differential diagnosis between sporadic and syndromic tumours appears not crucial, our results shed light on the possible link between SHH dysfunction and calretinin expression in GGS-related tumours.

Conservative management is effective in unicystic ameloblastoma occurring from the neonatal period: A case report and a literature review

Unicystic ameloblastoma (UA), a benign odontogenic tumor of the jaw, represents less than a third of all ameloblastomas and seems less aggressive than other types of ameloblastoma. We present here the first case of UA that developed prenatally and was successfully managed in the early neonatal period with marsupialization and curettage performed carefully to avoid injury to the tooth germ. BRAF and SMO mutations were not detected. After 2 years of follow-up, complete reossification and normal eruption of deciduous teeth were noted, and there was no recurrence of UA. We recommend conservative treatment of UA in the pediatric population to avoid loss of and/or injury to the tooth germ, provided close follow-up is carried out all through the individual's growth for early detection of potential recurrences, growth impairments, or tooth eruption disorders. The intratumoral somatic mutational status of BRAF, SMO, RAS family, and FGFR2 may help determine personalized targeted treatment, particularly in case of recurrence.

The dilemma of extensive unilocular radiolucent lesions of the jaws - value of immunohistochemistry as a diagnostic marker and prognostic Indicator

INTRODUCTION

Large Unilocular radiolucent lesions of the jaws often present a dilemma to both, the Oral Pathologist and the Maxillofacial surgeon with regards to their accurate diagnosis as well as their most appropriate treatment modality. A precise identification as to whether the lesion is a cyst or a tumor is imperative before any treatment is instituted. Once the correct diagnosis and likely prognosis are established, a management protocol can be planned which will completely eliminate the lesion, while at the same time, ensure least possible morbidity for the patient, such as pathological jaw fractures, persisting neurological deficits, esthetic deformity, functional debility, recurrence/persistence of the lesion, etc. AIM & OBJECTIVES: To establish the value of Immunohistochemistry (IH) as a Diagnostic marker and Prognostic indicator for extensive Unilocular radiolucent lesions of the jaws. To assess its role as an adjunct to Histopathological Examination (HPE) in distinguishing Odontogenic tumours from the cysts, by identifying the former using IH Tumor Markers; and in aiding in selection of the most appropriate and effective treatment option for each of such ambiguous lesions, based on their prognosis as indicated by the expression of lH Cell Proliferation Markers.

MATERIALS AND METHOD

Thirty cases of large Unilocular Radiolucent lesions of the jaws (Maxilla/Mandible) were managed over a period of three years. Histopathological examination (HPE) and Immunohistochemical (IH) analysis were carried out of the biopsy specimens in all the cases. Calretinin, an Immunohistochemical Tumor marker, was used to distinguish between Odontogenic cysts and tumours. Ki-67 and Proliferating Cell Nuclear Antigen (PCNA), Immunohistochemical Cell Proliferation markers, provided information on the aggressive potential of the lesions. On the basis of the above information, an appropriate management protocol was established for each of these different lesions. Nerve sparing enucleation and curettage was employed for the established cases of Odontogenic Cysts; Enucleation and curettage, peripheral ostectomy, followed by chemical cauterization was employed for the Unicystic Ameloblastomas and other Odontogenic tumours with a low Ki-67 and PCNA Proliferation Index (PI)/Labelling index (LI ≤ 3); Marginal resection was carried out for the tumours with a higher Labelling Index (LI >3 ≤5), and Segmental resection (including partial/complete Maxillectomy, Hemimandibulectomy with/without disarticulation) for the aggressive pathologies with high Labelling Index (LI > 5).

RESULTS

Of the thirty cases of large Unilocular radiolucent lesions of the Maxilla and Mandible, thirteen were diagnosed as Dentigerous cysts, one as Dentigerous cyst showing Ameloblastomatous transformation; two as Unicystic Ameloblastomas, one as the Mural variant of Unicystic Ameloblastoma; four as Follicular Ameloblastomas, two as Plexiform Ameloblastomas; four as Acanthomatous Ameloblastomas; one as Ameloblastic Fibroma and two as Adenomatoid Odontogenic Tumours. The predictive and prognostic indication of the Immunohistochemical markers correlated well with the post treatment findings.

CONCLUSION

In cases of extensive Unilocular lesions of the jaws, where ambiguity often exists in both diagnosis and appropriate treatment plan to be employed, Immunohistochemistry can serve as an invaluable tool in establishing the precise diagnosis, guiding the treatment plan, as well as indicating the likely prognosis of these lesions.

Calretinin expression in odontogenic cysts and odontogenic tumors and the possible role of calretinin in pathogenesis of ameloblastoma

Introduction:

Histopathological diagnosis of odontogenic cysts and tumors is a task mostly accomplished with hematoxylin and eosin staining. However, the use of additional diagnostic modalities such as immunohistochemistry may be necessary in histologically similar lesions. The reports of studies which have used calretinin as an immunohistochemical marker for ameloblastoma have been conflicting.

Aim:

The aim of the study was to evaluate the use of calretinin as a specific diagnostic marker for ameloblastoma and observe its expression in odontogenic cysts and other odontogenic tumors.

Materials and Methods:

Formalin-fixed, paraffin-embedded sections were taken from the archives which included 15 cases each of dentigerous cyst, radicular cyst, odontogenic keratocyst and ameloblastoma five cases of adenomatoid odontogenic tumor and three cases of ameloblastic carcinoma. Immunohistochemistry was done with calretinin antibody.

Results:

All ameloblastomas were positive for calretinin, whereas no other tumor or cyst showed positivity. Differences in proportion of calretinin expression were statistically significant with P = 0.000.

Conclusion:

Calretinin can be considered as a specific marker for ameloblastomas.

Glypican-3 distinguishes aggressive from non-aggressive odontogenic tumors: a preliminary study

BACKGROUND

Glypican-3 is a cell surface proteoglycan that is found in embrionary tissues, and there are no studies investigating this protein in odontogenic tumor. Thus, the aim of this study was to investigate glypican-3 in a series of aggressive and non-aggressive odontogenic tumors.

METHODS

Fifty-nine cases of tumors were divided into aggressive odontogenic tumors (20 solid ameloblastomas, four unicystic ameloblastoma, 28 KOTs including five associated with Gorlin-Goltz syndrome) and non-aggressive odontogenic tumors (five adenomatoid odontogenic tumors and two calcifying cystic odontogenic tumors) and analyzed for glypican-3 using immunohistochemistry.

RESULTS

Glypican-3 was observed in seven solid ameloblastoma and eighteen keratocystic odontogenic tumors including three of the five syndromic cases, but there was no significant difference between syndromic and sporadic cases (P > 0.05; Fisher's exact Test). All cases of unicystic ameloblastoma (n = 4), adenomatoid odontogenic tumor (n = 5), and calcifying cystic odontogenic tumor (n = 2) were negative.

CONCLUSIONS

This provided insights into the presence of glypican-3 in odontogenic tumors. This protein distinguished aggressive from non-aggressive odontogenic tumors.

Dentigerous Cyst and Ameloblastoma of the Jaws

AIM

To determine how many ameloblastomas were misdiagnosed as dentigerous cysts (DCs) by correlating the radiological and histopathological features of a series of both entities.

METHODS AND RESULTS

Histopathology reports and radiological imaging of 135 DCs and 43 ameloblastomas were reviewed. Any clinical or radiological feature that suggested that the diagnosis of DC was wrong-for example, absence of an unerupted tooth-prompted review of the original histology. A total of 34 cases coded as DC at diagnosis were excluded; in the remaining 101 patients, the clinicoradiological and histopathological features were consistent with DC in 96 (95.0%). Review of the histology revealed that 4 patients had actually had odontogenic keratocysts (OKCs) and one a luminal/simple unicystic ameloblastoma (UA). One other OKC and 3 other ameloblastomas (1 luminal UA, 2 solid/multicystic) had originally been diagnosed as DC; these had been identified prior to the study. Of the 9 misdiagnosed patients, 6 were ≤20 years old. Clinically, DC had been the only, or one of the differential, diagnoses in 7 patients; in the other 2, the clinical diagnosis was radicular cyst. In none of the 4 misdiagnosed ameloblastomas was the radiology compatible with a diagnosis of DC. Incorrect terminology had been used on the histopathology request form in 5 of the 34 excluded cases where the clinical diagnosis was DC, despite the cyst being periapical to an erupted carious or root-filled tooth.

CONCLUSIONS

The entire clinical team must ensure that a histopathological diagnosis of DC is consistent with the clinicoradiological scenario, particularly in younger patients.

Recurrent giant mandibular ameloblastoma in young adults

BACKGROUND

The purpose of the study was to define the most appropriate management of the giant mandibular ameloblastoma (GMA) in young adults.

METHODS

A retrospective study was performed on patients with GMA <30 years old. The data collected included initial treatment, tumor margins, reconstruction, and follow-up. Patients evaluated speech, chewing, swallowing, and facial appearance after definitive treatment.

RESULTS

Thirteen patients were identified with recurrent solid/multicystic disease requiring further treatment. Definitive treatment involved segmental mandibulectomy and reconstruction with free fibular flap in all patients. Seven patients had immediate reconstruction (group A) and 6 had secondary (group B). Mandibular resection was planned at least 2 cm beyond the radiological limit, free margins were achieved in all patients, and all flaps were transplanted successfully. In group A, functional score was 13.7 ± 0.45 and facial appearance score was 4.5 ± 0.49, whereas in group B were 11.16 ± 0.37 and 3.3 ± 0.5, respectively (both p < .05).

CONCLUSION

Aggressive resection of the GMA and immediate reconstruction is strongly advised. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1947-E1954, 2016.

Primordial Odontogenic Cyst with Induction Phenomenon (Zonal Fibroblastic Hypercellularity) and Dentinoid Material Versus Archegonous Cystic Odontoma: You Choose!

The most recent A.F.I.P. fascicle defines primordial odontogenic cyst (POC) as a distinct, nonkeratinized, odontogenic cyst of "undetermined origin" forming in the place of a developing normal or supernumerary tooth. However, the majority of examples reported in the literature under this term represent odontogenic keratocysts (keratocystic odontogenic tumors). In addition, there are rare reported cases of cystic odontomas. An 18-year-old Caucasian male presented with a unilocular mandibular radiolucent lesion in the place of a congenitally missing molar. Histologically, it featured nonkeratinizing, thin stratified squamous epithelial lining with areas of spongiosis and foci of vacuolization of individual basal cells without significant nuclear palisading. Focally, budding of the basal cell layer was identified. A zone of increased cellularity featuring induction-type fibroblasts was present subepithelially as well as dentinoid deposits with odontogenic epithelial nests. Immunohistochemically, the epithelial lining was negative for calretinin and the induction-like zone negative for S100 protein, smooth muscle actin, and CD34. The case was externally reviewed by five oral pathologists who provided various diagnostic interpretations including primordial cyst, odontogenic cyst not otherwise specified (NOS), cyst with ameloblastic changes, and unicystic ameloblastoma. At that time, a final diagnosis of odontogenic cyst NOS was rendered with a comment that it may represent a true example of POC or a cystic odontoma. The lesion has not recurred within a 13 year follow-up period after initial excision. An unusual cystic lesion is presented that may represent a true example of POC with dentinoid formation or an archegonous cystic odontoma.

The diagnostic usefulness of immunohistochemistry for odontogenic lesions

The diagnosis of odontogenic tumors can be challenging, largely due to their rarity and consequent difficulties in gaining experience in their assessment. In most cases, careful attention to morphology, in conjunction with clinical and radiological features will allow a diagnosis to be made. However, in some cases, immunohistochemical analysis of the tumor may be useful. In this review we will outline the immunohistochemical expression profile of normal developing odontogenic tissues and a range of odontogenic tumors. In many cases the immunohistochemical markers are neither specific nor sensitive enough to be of help in diagnosis, but in some cases such analysis may prove very useful. Thus we have outlined a limited number of circumstances where immunohistochemistry may be of use to the practicing diagnostic pathologist.

Calretinin as a diagnostic adjunct for ameloblastoma

Background. Calretinin is a 29 kDa calcium-binding protein of the EF-hand family which is expressed in a variety of normal and tumorigenic tissues. Its expression in odontogenic epithelium during odontogenesis and in neoplastic odontogenic tissues has been demonstrated. Unicystic ameloblastoma poses a diagnostic challenge, as its histologic presentation can be sometimes mistaken for keratocystic odontogenic tumor (KCOT). This study was performed to assess the usefulness of calretinin as a confirmatory marker for ameloblastic tissue. Methodology. Total of 40 cases: 16 unicystic ameloblastoma, 4 multicystic ameloblastoma, and 20 KCOT, were evaluated immunohistochemically for the presence, localization, distribution, and intensity of calretinin expression. Statistical analysis was done using Chi-square test to intercompare the expression between ameloblastoma and KCOT. Results. Sixteen cases of ameloblastoma (12 unicystic, 4 multicystic) showed positive calretinin staining of ameloblastic epithelium and only one case of KCOT was positive for calretinin, with the positivity restricted to the stellate reticulum like epithelium. Intercomparison between two groups revealed statistically significant difference (P = 0.000). Conclusion. Calretinin appears to be a specific immunohistochemical marker for neoplastic ameloblastic epithelium and may be an important diagnostic adjunct in the differential diagnosis of ameloblastoma and KCOT.

Diagnostic dilemma of unicystic ameloblastoma: novel parameters to differentiate unicystic ameloblastoma from common odontogenic cysts

AIM

Diagnostic criteria that have been specified for unicystic ameloblastomas (UAs) are not always helpful to differentiate these cystic tumors from common odontogenic cysts. The aim of this study therefore was to identify additional histopathological features (other than the features considered for the diagnosis of UA at present) that would be helpful to differentiate UA from odontogenic cysts.

METHODS

One hundred histopathologically confirmed unicystic ameloblastomas and 20 cases each of radicular, inflamed dentigerous and non-inflamed dentigerous cysts were selected. Histopathological features of the UAs that are not used as diagnostic criteria at present were identified.

RESULTS

Hyperplastic arcading epithelial proliferations with stellate-reticulum-like and vacuolated cells were always seen associated with inflammation in odontogenic cysts, while in UA plexiform-like areas were also seen without inflammation (P < 0.001). In addition, a spiky rete pattern was observed in non-inflamed UA while this pattern was observed only in inflamed odontogenic cysts. Furthermore, spiky retes together with subepithelial hyalinization were usually observed in UAs while only subepithelial hyalinization was observed in non-inflamed dentigerous cysts.

CONCLUSIONS

Combinations of histopathological features were identified to differentiate non-inflamed UA from common odontogenic cysts. However, presence of inflammatory changes in UA precludes the use of features identified in the present study for diagnostic purposes.

Multilocular unicystic ameloblastoma of mandible

Introduction. We report a rare case of unicystic ameloblastoma (UA) of mandible which showed multilocular radiolucency on the left side of mandible on radiographic examination which is very unusual, and the majority of the cases of UAs till date has been reported of unilocular radiolucency. On histopathological examination, an odontogenic cystic lining that proliferates that intraluminally resembling ameloblastomatous epithelium was observed, leading to a definitive diagnosis of unicystic ameloblastoma. Case Presentation. A 42-year-old male patient presented with a swelling on the left side of the mandible extending from 33 to 36. Radiographically, it showed a multilocular radiolucent lesion resembling odontogenic cyst; however, the final diagnosis was made on histopathological ground with the inclusion of radiological and clinical features. Conclusion. It can be concluded that at present, histopathologic examination is the most sensitive tool for differentiating between odontogenic cysts and UAs. However, both clinical and radiologic findings share equal contribution to the final diagnosis.

Treatment of recurrent mandibular ameloblastoma

Ameloblastoma is a locally invasive benign odontogenic tumor with a high rate of recurrence in the long term. The authors conducted a retrospective study of patients with mandibular ameloblastoma in order to evaluate recurrent ameloblastoma management. The study included data from 31 patients over a period of 10 years. Data collected included age, gender, tumor location, histological findings, initial treatment, number of recurrences and year of onset, type of treatment of recurrence, reconstruction and follow-up. Recurrences were detected in nine patients (29%). Tumor recurrences appeared at 32 months on average following the initial surgical procedure. Recurrences were associated mainly to inadequate initial therapeutic approach and were treated by bone resection with a safety margin of at least 1 cm beyond the radiographically visible margins. Immediate reconstruction of bone defects was performed with grafts or free flaps.

Exclusion of all three calbindins from a calcium-ferry role in rat enamel cells

It is widely accepted that healthy enamel formation depends on a steady supply of calcium, yet only fragmentary understanding exists about the mechanisms underlying transepithelial calcium transport. Several lines of evidence indicate that calcium principally follows a transcellular route, which classically is thought to be facilitated by cytosolic calcium-binding proteins termed calbindins. In enamel cells, however, this 'calcium-ferry' dogma appears to fail as we previously found that the major calbindin in murine enamel cells (calbindin-28 kDa) was down-regulated during the peak period of calcium transport and enamel was formed normally in mice lacking calbindin-28 kDa. It remains to be clarified whether the two other known calbindins could function as calcium ferries instead. This study used biochemical and proteomic approaches to obtain definitive identification and quantification of the 30-kDa calbindin (calretinin) and calbindin-9 kDa (S100-G) in enamel epithelium from rat. By establishing that both of these calbindins contribute insufficient calcium capacities in molars and incisors, our results render the calcium-ferry dogma untenable. Of significance to enamel defects and dental bioengineering, these findings support other evidence for an alternative organelle-based mode of calcium transport (calcium transcytosis) and also implicate S100-G/calbindin-9 kDa, but not calretinin, in a calcium-signaling role during enamel maturation.

Histopathology of ameloblastoma of the jaws; some critical observations based on a 40 years single institution experience

The aim of the present study is to examine all cases of intraosseous benign ameloblastomas treated between 1970 and 2010 in a single institution and to look for a possible correlation between the histopathological aspects and the demographical and clinical parameters, as well as the treatment outcome. The data of a total number of 44 patients were retrieved from the records. Nine patients were excluded because of doubt about the correct diagnosis (8 patients) or because of an extra-osseous presentation (1 patient). No statistically significant differences were found between the histopathological (sub)types of ameloblastomas and the demographical and clinical parameters, nor between the histopathological (sub)types and treatment outcome. Of the 28 patients treated by enucleation, in 17 patients one or more recurrences occurred, with no significant predilection for any histopathological (sub)type, including the unicystic type. There were no significant differences in the recurrence rate after enucleation in patients below and above the age of 20 years either. In six out of 17 patients with a recurrence, the recurrent lesion showed a different histopathological subtype than was encountered in the primary. In two cases a change from solid/multicystic to desmoplastic ameloblastomas was noticed. In conclusion, the current histopathological classification of benign intraosseous ameloblastoma does not seem to have clinical relevance with the possible exception of the luminal unicystic ameloblastoma that has been removed in toto, unfragmented. Since no primary desmoplastic ameloblastomas were encountered in the present study no further comments can be made on this apparently rare entity.

Key words: Odontogenic tumours, ameloblastoma, histopathology.

The Ca(2+)-binding protein calretinin is selectively enriched in a subpopulation of the epithelial rests of Malassez

During tooth development, the inner and outer enamel epithelia fuse by mitotic activity to produce a bilayered epithelial sheath termed Hertwig's epithelial root sheath (HERS). The epithelial rests of Malassez (ERM) are the developmental residues of HERS and remain in the adult periodontal ligament (PDL). Although the cellular regulation of the Ca(2+)-binding proteins parvalbumin, calbindin-D28k, and calretinin has been reported in the inner and outer enamel epithelia during tooth development, an involvement of Ca(2+)-binding proteins in the ERM has not so far been characterized. Among the three Ca(2+)-binding proteins tested (calbindin D28k, parvalbumin, calretinin), we have only been able to detect calretinin in a subpopulation of adult rat molar ERM, by using quantitative immunohistochemical and confocal immunofluorescence techniques. TrkA (a marker for ERM) is present in numerous epithelial cell clusters, whereas calretinin has been localized in the cytosol and perinuclear region of a subpopulation of TrkA-positive cells. We conclude that, in inner and outer enamel epithelial cells, Ca(2+) is regulated by calbindin, parvalbumin, and calretinin during tooth development, whereas in the ERM of adult PDL, Ca(2+) is regulated only by calretinin. The expression of Ca(2+)-binding proteins is restricted in a developmental manner in the ERM.

CD56 (NCAM) expression in ameloblastomas and other odontogenic lesions

AIMS

  Ameloblastomas recapitulate certain elements of tooth formation. CD56 is expressed by a variety of cells and is used in tumour diagnosis, but is also expressed in the enamel organ during tooth development. The aim of this study was to describe the expression of CD56 in odontogenic lesions with particular reference to the differential diagnosis of ameloblastoma and odontogenic keratocyst.

METHODS

  Cases were selected from the pathology archives at Glasgow Royal Infirmary, Glasgow, Royal Victoria Infirmary, Newcastle and Department of Diagnostic Sciences, Texas A&M Health Science Center Baylor College of Dentistry, Dallas. The study population included 38 ameloblastomas, 19 odontogenic keratocysts and a number of other odontogenic lesions, including nine compound odontomes. All sections were examined for CD56 immunoreactivity and the extent of staining was recorded.

RESULTS

  Thirty-seven of 38 (97%) ameloblastomas expressed CD56 on the cell membrane of peripheral cells in tumour nests (16 extensively, 21 focally). Immunoreactivity was lost in areas of inflammation, acanthomatous differentiation, in areas of cystic change and upon fusion with overlying surface epithelium. One odontogenic keratocyst expressed CD56 (5%, P < 0.0001). CD56 was expressed very focally in two odontomes, exclusively in stratum intermedium-like cells.

CONCLUSIONS

  CD56 expression in odontogenic epithelium is highly suggestive of ameloblastoma and can help in differentiating this from odontogenic keratocyst.

Review article: Current concepts of ameloblastoma pathogenesis

Ameloblastoma is a locally destructive and invasive tumour that can recur despite adequate surgical removal. Molecular studies have offered interesting findings regarding ameloblastoma pathogenesis. In the present review, the following topics are discussed regarding its molecular nature: clonality, cell cycle proliferation, apoptosis, tumour suppressor genes, ameloblastin and other enamel matrix proteins, osteoclastic mechanism and matrix metalloproteinases and other signalling molecules. It is clear from the literature reviewed that translational studies are necessary to identify prognostic markers of ameloblastoma behaviour and to establish new diagnostic tools to the differential diagnosis of unicystic from multicystic ameloblastoma. Finally, molecular biology studies are also important to develop more effective alternative approaches to the treatment of this aggressive odontogenic tumour.

An unusual ostensible example of intraoral basal cell carcinoma

An example of oral basal cell carcinoma is presented originating on the posterior mandibular mucosa and gingiva of a 67-year-old female. Histologically, it featured a multifocal pattern. It recurred eight times in a period of 20 years. Tissue samples of the tumor were evaluated with monoclonal antibody Ber-EP4 and were compared with examples of oral mucosa, skin, oral and cutaneous squamous cell carcinoma, peripheral ameloblastoma, ameloblastoma and cutaneous basal cell carcinoma (BCC). Only neoplastic basal cells showed positive immunohistochemical staining. Additionally, microdissected neoplastic areas were evaluated for loss of heterozygosity (LOH) of the PTCH gene with markers D9S303, D9S252 and D9S287. PTCH gene mutations are reported in patients with Gorlin syndrome and sporadic cutaneous BCCs. Loss of one allele was observed with all three markers. Examples of conventional ameloblastomas did not show evidence of LOH. These observations support the inclusion of BCC in the differential diagnosis of appropriate oral mucosal neoplasms.

Diagnostically challenging epithelial odontogenic tumors: a selective review of 7 jawbone lesions

Considerable variation in the clinicopathologic presentation of epithelial odontogenic tumors can sometimes be confusing and increase the chance of misdiagnosis. Seven diagnostically challenging jawbone lesions are described. There were 2 cases of mistaken identity in our ameloblastoma file. One unicystic type, initially diagnosed and treated as a lateral periodontal cyst, showed destructive recurrence 6 years postoperatively. The other globulomaxillary lesion was managed under the erroneous diagnosis of adenomatoid odontogenic tumor and recurred 4 times over an 11-year period. This tumor was found in retrospect to be consistent with an adenoid ameloblastoma with dentinoid. The diagnosis of cystic squamous odontogenic tumor (SOT) occurring as a radicular lesion of an impacted lower third molar was one of exclusion. Of two unsuspected keratocystic odontogenic tumors, one depicted deceptive features of pericoronitis, while the other case has long been in our files with the diagnosis of globulomaxillary SOT. Two cases of primary intraosseous squamous cell carcinoma appeared benign clinically and exhibited unexpected findings; an impacted third molar began to erupt in association with the growth of carcinoma and another periradicular carcinoma showed dentinoid formation. Cases selectively reviewed in this article present challenging problems which require clinical and radiographic correlation to avoid potential diagnostic pitfalls.

Comparative expression of calretinin in selected odontogenic tumours: a possible relationship to histogenesis

AIMS

Calretinin, a calcium-binding protein, is expressed primarily in certain subtypes of neurons. It has also been reported to be present in mesotheliomas and other tumours. The aim was to determine the expression of calretinin in selected odontogenic neoplasms.

METHODS AND RESULTS

Immunohistochemistry for calretinin was performed on 55 odontogenic tumours consisting of 20 solid ameloblastomas, five calcifying epithelial odontogenic tumours, 10 adenomatoid odontogenic tumours, 10 ameloblastic fibromas and 10 odontogenic myxomas. The distribution, intensity, pattern and localization of immunoreactive cells were determined by conventional light microscopy. chi(2) test was used for statistical analysis and P < 0.05 was considered to be significant. All 20 ameloblastomas showed intense immunopositivity with a diffuse distribution pattern. None of the other neoplasms was reactive with calretinin. Differences in the proportion of calretinin expression between groups were statistically significant at P < 0.001.

CONCLUSIONS

Considering that ameloblastomas, in contrast to the other studied tumours, were consistently reactive for calretinin, this protein may have a role in the pathogenesis of this aggressive neoplasm.

Adenomatoid odontogenic tumor (AOT) originating in a unicystic ameloblastoma: a case report

The follicular variant of the adenomatoid odontogenic tumor (AOT) is thought to originate from the reduced enamel epithelium of the dental follicle. The origin of the extra-follicular variant however, remains less clear. This paper presents a case of an extra-follicular AOT, which we believe originated from the epithelial lining of a unicystic ameloblastoma, and reviews the literature. The available evidence seems to indicate that some extra-follicular AOTs might arise as secondary phenomena within pre-existing odontogenic cysts or cystic tumors.

Dentigerous cyst versus unicystic ameloblastoma--differential diagnosis in routine histology

BACKGROUND

Unicystic ameloblastomas (UAs) and dentigerous cysts (DCs) have an identical clinical and radiographic appearance. Some subtypes of UAs have a better prognosis than solid or multicystic ameloblastomas, and simple enucleation is the adequate treatment. The present study was designed to test the hypothesis that UAs with small islands of ameloblastomatous epithelium may be misdiagnosed as a DC or keratocyst if no more than two histologic sections are examined.

METHODS

A total of 101 resection specimens from 22 women and 73 men (mean age: 46.5 years) were selected, all showing the clinical and radiographic features of a DC. Only cysts with a minimum diameter of 15 mm in the panoramic X-ray were considered for the present investigation. The histopathologic diagnosis had been routinely established by examining two sections. For our study, the specimens were investigated by step sections at 50 microm and by staining of 5 microm thin sections with hematoxylin and eosin (H&E) at 1 mm levels. An average of 15 slides were evaluated per case.

RESULTS

Microscopic examination of the step sections did not reveal ameloblastomatous epithelium in the cyst lining epithelium of the 101 cases. Thus, every primary diagnosis of a dentigerous cyst was confirmed. In four cases, additional rather large odentogenic cell nests were detected with palisading of basaloid cells, while there was a lack of other signs of ameloblastic differentiation. All lesions were completely resected, and no additional treatment was performed.

CONCLUSIONS

Step sectioning of larger DCs may reveal associated odontogenic cell nests in some cases but does not lead to the detection of formerly missed ameloblastic cells. Thus, unicystic ameloblastomas are not misdiagnosed if only two slides are prepared for routine diagnosis of DCs.

Calretinin expression in odontogenic cysts

Calretinin is a calcium-binding protein with a possible role as a calcium buffer, calcium-sensor, or regulator of apoptosis. Calretinin is expressed in neural tissue, is a specific marker of mesothelial cells, and has been demonstrated in the odontogenic epithelium during odontogenesis in rat molar tooth germs. Moreover, it has been found to be expressed in a high proportion of solid, unicystic, and multicystic ameloblastomas, whereas, on the contrary, no positive staining has been found in odontogenic keratocysts, residual cysts, and dentigerous cysts. The purpose of this study was to evaluate calretinin expression in radicular cysts, follicular cysts, orthokeratinized keratocysts, and parakeratinized keratocysts. A total of 70 odontogenic cysts, 24 radicular cysts, 24 follicular cysts, and 22 odontogenic keratocysts (10 orthokeratinized keratocysts, 12 parakeratinized keratocysts) were evaluated. All the radicular cysts, follicular cysts, and orthokeratinized keratocysts were negative. However in 8 of 12 parakeratinized keratocysts, there was a positivity to calretinin in the parabasal-intermediate layers of the cyst epithelium. This positivity to calretinin in the parabasal layers in parakeratinized keratocysts, similar to that found for other markers like PCNA and p53, could point to an abnormal control of the cell cycle and could help to explain the differences in the clinical and pathologic behavior of odontogenic keratocysts, in particular the differences found between orthokeratinized keratocysts and parakeratinized keratocysts.

The spatial and temporal expression of calretinin in developing rat molars (Rattus norvegicus)

Calretinin is a 29-kDa calcium-binding protein abundantly expressed in central and peripheral neural tissues. The aim here was to determine its expression during various stages of odontogenesis. Five categories of embryonic (E) and postnatal (P) rats at various ages (E17, E18, E20, P0, and P7), both male and female, were used to represent the various stages of molar tooth development. The heads of the experimental animals were harvested at the appropriate time and each was cut mid-sagittally and coronally to locate the tooth germs. Selected sections were stained immunohistochemically with polyclonal rabbit anticalretinin at a concentration of 1:25 after microwave irradiation. The results showed that calretinin is distributed widely in epithelium-derived tissues during odontogenesis in rat molar tooth germs. It was expressed focally in the dental lamina, outer enamel epithelium, stellate reticulum and stratum intermedium at different stages. In contrast, it was expressed diffusely and intensely in the inner enamel epithelium and presecretory ameloblasts, although it was discontinuous over the cusp tips. In the secretory ameloblasts, the staining was less intense, being restricted to the cytoplasm, including Tomes' processes. This distribution suggests that calretinin may play a part in enamel formation.