Conceptual changes in ameloblastoma: Suggested re-classification of a "veteran" tumor.

OBJECTIVES: The merging of ameloblastoma (AM) with mural unicystic ameloblastoma (UAM-M) was suggested by the 2017 WHO based on similar treatment needs. In an international multicenter study, we investigated the characteristics of their merged product (merged-AM) and raised the possibility of unifying AM and UAM (total-AM). MATERIALS AND METHODS: AM and UAM (luminal/intraluminal/mural), separate and combined, were analyzed for demographic/clinical/radiological features. ANOVA and chi-square tests were followed by univariate and multivariate analyses, and significance was set at p < .05. RESULTS: The patients' mean age was 39.6 ± 20.3 years in merged-AM (147 AM, 76 UAM-M), 45.1 ± 19.4 years in AM (p = .009). Merged-AM comprised 51.3% multilocular/48.7% unilocular tumors, AM comprised 72.5%/27.5%, respectively (p < .001). Merged-AM was associated with impacted teeth in 30.8%, AM in 18% (p = .023). The probability of merged-AM for multilocularity increased by 2.4% per year of age (95%CI 0.6-4.2, p = .009). Association with impacted teeth decreased by 7.9% per year of age (95%CI 1.9-14.39, p = .009). Merged-AM did not differ from total-AM (p > .05). CONCLUSIONS: Merged-AM partially differed from AM, but differences appeared to diminish in an age/time-wise manner. Merged-AM and total-AM were nearly indistinguishable. Therefore, AM and UAM may be considered a continuous spectrum of one type of tumor, further necessitating revision of the treatment approaches.

Expression of stem cell markers in stroma of odontogenic cysts and tumors.

BACKGROUND: The stroma of odontogenic cysts/tumors may confer them differential biological behavior. We aimed to investigate the immunoexpression of stem cell markers (Nanog, SOX2, Oct4, and CD34) in the stroma of odontogenic cysts and tumors. CD34 was investigated exclusively as a marker for stromal fibroblast/fibrocyte cells (CD34 + SFCs). CD34 + SFCs were also investigated ultrastructurally. METHODS: Ten cases each of primary odontogenic keratocyst (OKC), recurrent OKC, dentigerous cyst, ameloblastoma, unicystic ameloblastoma, odontogenic myxoma, and 7 syndromic OKC were included. Results were represented as the mean score (%) of positive cells/field for each marker for each study group. For CD34 + SFCs, results are presented as the mean number of cells/field for each type of lesion. Kruskal-Wallis and Spearman's correlation statistical tests were used; significance was set at P < .05. RESULTS: All markers except Oct4 were expressed by stromal cells in all lesions. Expression of SOX2 was significantly higher in tumors than in cysts (P < .05). CD34 + SFCs were more frequent in cysts than in tumors. Ultrastructurally, CD34 + SFCs were identified for the first time in odontogenic lesions and showed characteristic bipolar/dendritic morphology. CONCLUSION: Among examined stromal stem cell markers, only SOX2 distinguished tumors from cysts. CD34 + SFCs may also contribute to the biological behavior of odontogenic lesions.

Central Dentinogenic Ghost Cell Tumor: An Update on a Rare Aggressive Odontogenic Tumor.

PURPOSE: Dentinogenic ghost cell tumor (DGCT) is a very rare odontogenic lesion, with most knowledge based on single case reports. Therefore, a comprehensive analysis was performed of the clinical and radiologic features of reported cases of DGCT with an emphasis on treatment modalities. MATERIAL AND METHODS: This is a case series of DGCTs collected from the literature after a systematic search of Medline's PubMed and Google Scholar. Three additional cases were included from the authors' files. Demographic data of the patients, lesion site and size, and radiologic features were analyzed. Treatment approach and events of recurrence were recorded. RESULTS: Forty-five cases (42 from the literature) were included. The mean age of patients was 39.7 ± 19.3 years (range, 12 to 79 yr) and the male-to-female ratio was 1.8:1. The mandible-to-maxilla ratio was 1.14:1, with the posterior region of the jaws being the most commonly involved site. Radiographically, 78% lesions were unilocular, 67% were mixed radiolucent and radiopaque, and 68% had well-defined borders. The mean lesion size was 4.0 cm (range, 1.8 to 13.0 cm). The primary treatment for 21 patients was conservative surgery consisting of enucleation or curettage. Follow-up information for longer than 1 year (mean, 6.2 ± 8.3 yr; range, 1 to 31 yr) was known for 15 patients, of whom 11 (73%) had recurrences. The primary treatment in 19 patients was radical surgery consisting of marginal or segmental resection. Follow-up information for longer than 1 year (mean, 3.3 ± 2.6 yr; range, 1 to 10 yr) was known for 12 patients, of whom 4 (33%) had recurrences. CONCLUSIONS: This study highlighted the potentially aggressive biological behavior of DGCTs that demands extensive surgery and long follow-up. However, owing to the rarity of DGCT, more well-documented cases with long follow-up periods are needed to further define the optimal treatment modalities and prognosis.

Relative frequency of localized reactive hyperplastic lesions of the gingiva: a retrospective study of 1675 cases from Israel.

BACKGROUND: The gingiva reacts to chronic irritation or trauma with localized reactive hyperplastic lesions (LRHL) that can be classified into four groups: focal fibrous hyperplasia (FFH), pyogenic granuloma (PG), peripheral ossifying fibroma (POF), and peripheral giant cell granuloma (PGCG). This study determined the frequency of LRHL in an oral pathology biopsy service and compared these data with reports from other countries. METHODS: The material included the biopsies of all consecutive LRHL of the gingiva stored in the departmental database (1989-2008). Lesions were analyzed according to their location and to the patients' age and gender. The findings were compared with those published in studies from other countries. RESULTS: There were 1675 LRHL that comprised 6.7% of the 25,106 accessed biopsies. FFH was the most common (31.8%), followed by PG (29.1%), POF (20.4%), and PGCG (18.7%). POF tended to affect younger patients than did FFH, PG, and PGCG. FFH, PG, and POF were more common in women, while PGCG showed no gender predilection. PG and POF were more common in the maxilla, PGCG more common in the mandible and FFH was distributed equally between the jaws. The anterior region of the maxilla was the most prevalent site for FFH, PG, and POF. CONCLUSION: The results of this study differ somewhat from those of other countries. There is a need for further investigation to answer the question whether the differences can be attributed to geographic or ethnic factors and/or to small sample sizes of the reported studies.

Pediatric localized reactive gingival lesions: a retrospective study from Israel.

PURPOSE: Chronic irritation of the gingiva causes localized reactive hyperplastic lesions (LRHLs), which are classified into: peripheral ossifying fibroma (POF); peripheral giant cell granuloma (PGCG); pyogenic granuloma (PG); and focal fibrous hyperplasia (FFH). The purpose of this study was to determine the frequency of localized reactive hyperplastic lesions in Israeli children and adolescents. METHODS: All consecutive archival LRHL biopsies of the gingiva between 1989 and 2008 were included. Lesions were analyzed according to location and patients' age and gender. Our findings were compared to pediatric and all-age data in publications from other countries. RESULTS: Of 233 gingival LRHL specimens, POFs were most common (33%), followed by PGs (25%), FFHs (23%) and PGCGs (20%). PGs and FFHs were more common in females, and PGCG were more common in males. POFs showed no gender predilection. PGCGs and FFHs were distributed almost equally between the maxilla and mandible, while POFs and PGs were more common in the maxilla. Comparing data to other countries was problematic because there were so few dedicated to the pediatric population and because of inconsistencies in data presentation. CONCLUSIONS: Pediatric dentists should be aware of gingival LRHLs, because they are not uncommon among children.

Metaplastic changes in the epithelium of radicular cysts: A series of 711 cases.

BACKGROUND: This study was aimed to evaluate the prevalence of metaplastic changes in the epithelium of radicular cysts and to investigate how they relate to the clinical and radiographic characteristics of the cysts, based on a large series of radicular cysts. MATERIAL AND METHODS: Biopsies of cysts of endodontic origin that were examined at the Department of Oral Pathology between 2004 and 2011 have been re-evaluated for this study. Only cases that were re-confirmed with clinical and histological diagnoses of a radicular or residual radicular cyst were included. The included cases were evaluated for the prevalence of metaplastic changes in the form of mucous secreting cells (MSC) or ciliated cells (CC). The relations between the metaplastic changes and the cyst type (radicular or residual radicular), as well as demographic, clinical and radiographic parameters, were statistically evaluated using Fischer and chi-square tests. Significance was set at p<0.05. RESULTS: A total of 711 cysts were included: 677 were radicular cysts (95%) and 34 (5%) were residual radicular cysts. 23 cases had histopathological diagnoses other than radicular or residual radicular cysts and were excluded from the study. MSC were present in 47 (6.6%) cysts. MSC were significantly more common in residual radicular cysts than in radicular cysts [8 (23.5%) and 39 (5.8%), respectively; p<0.001]. MSC-containing cysts were commonly found in asymptomatic patients (10.5%, p<0.001), and usually presented with well-defined radiographic borders (7.2%, p<0.05). CC were present in 34 (4.8%) cysts, with a markedly high prevalence in the maxillary molar sextant (15%, p<0.001). CONCLUSIONS: In the epithelium of radicular and residual radicular cysts the presence of specific metaplastic changes may be related to cyst type, symptomatology, radiographic findings and tooth location. Key words:Radicular cyst, metaplasia, mucous secreting cells, ciliated cells.

Myofibroblasts in stroma of odontogenic cysts and tumors can contribute to variations in the biological behavior of lesions.

Stromal myofibroblasts (MF) have the potential to facilitate progression of neoplastic epithelial lesions that could contribute to their biological behavior. To assess immunohistochemically the frequency of stromal MF in different odontogenic cysts and tumors and correlate it to their aggressive biological behavior. The study included cases of dentigerous cyst (DC, n = 7), odontogenic keratocyst-parakeratinized type (OKC-P, n = 8), orthokeratinized type (OKC-O, n = 9), ameloblastic fibroma/fibro-odontoma (AMF/O, n = 11), unicystic ameloblastoma (UAM, n = 6), and solid ameloblastoma (SAM, n = 7). Cases of oral squamous cell carcinoma (SCC, n = 5) served as control. Myofibroblast frequency was assessed as the number of alpha smooth muscle actin (alphaSMA)-positive stromal cells in 10 high-power fields, presented as the mean number of positive cells per field. Counts showed that mean number of positive cells in OKC-P (25.7+/-11.4) was significantly higher than in DC (8.7+/-11.6) (p = 0.024) and in SAM (29+/-7) it was significantly higher than in UAM (14.9+/-4.9) and AMF/O (5.6+/-7.5) (p < 0.001). Counts in OKC-P and SAM were not significantly different from SCC (21.3+/-5.3) (p > 0.05). The high frequency of stromal MF in known aggressive odontogenic lesions, such as OKC-P and SAM, implies that MF can contribute to the biological behavior of these odontogenic lesions. Various pharmacological agents that control stromal MF can be used as an aid to reduce extensive and mutilating surgery in cases of remarkably aggressive odontogenic lesions.

Histopathological spectrum of bone lesions associated with dental implant failure: osteomyelitis and beyond.

Early or late post-implant placement complications are usually localized infectious/inflammatory processes and treated accordingly. If the healing process does not take place within a reasonable timeframe, the possibility of a pathologic process beyond localized infection/inflammation should be suspected. We describe a radiological/histopathological spectrum of bony lesions ranging from inflammatory to malignant lesions surrounding failed dental implants. Five cases of mandibular dental implant failure that clinically, radiologically and histopathologically appeared to be inflammatory processes are presented. The failure of the dental implants was immediate in two cases and late in the remaining three. The radiological features were essentially similar for all five, and they included radiolucent or mixed radiolucent-radiopaque lesions with poorly defined borders. Three lesions were limited to the area of the failed implant, while the other two extended to a large part of the mandible. The histopathological findings ranged from acute osteomyelitis and chronic osteomyelitis with features of a fibro-osseous-like lesion and occasional rimming of atypical osteoblasts to osteogenic sarcoma that was admixed with a component of osteomyelitis (diagnosis of the latter was achieved only after a series of biopsies). In-depth investigative procedures are imperative in order to establish an accurate diagnosis whenever the histopathological diagnosis is inconsistent with persisting clinical signs and symptoms in bone lesions associated with failed dental implants.

Ameloblastic fibroma: a stage in the development of a hamartomatous odontoma or a true neoplasm? Critical analysis of 162 previously reported cases plus 10 new cases.

OBJECTIVE: To analyze neoplastic and hamartomatous variants of ameloblastic fibromas (AFs). STUDY DESIGN: Analysis of 172 cases (162 previously reported, 10 new). RESULTS: AF emerged as a lesion primarily of children and adolescents (mean age, 14.9 years), with about 80% diagnosed when odontogenesis is completed (age, < 22 years). Around 28% of all AFs were small and asymptomatic, and 72% exhibited moderate-to-severe bone expansion. CONCLUSIONS: There are 2 variants of AF: neoplastic and hamartomatous. Lesions in patients aged >22 years are considered true neoplasms, while those in younger patients may be either true neoplasms or odontomas in early stages of development. Although the histopathology of hamartomatous and neoplastic variants of AF are indistinguishable, clinical and radiologic features can be of some help to distinguish between them. Asymptomatic small unilocular lesions with no or minimal bone expansion in young individuals are likely to be developing odontomas, and large, expansile lesions with extensive bone destruction are neoplasms.

Clinical and radiological profile of ameloblastic fibro-odontoma: an update on an uncommon odontogenic tumor based on a critical analysis of 114 cases.

Ameloblastic fibro-odontoma is an uncommon benign tumor of the jaws that belongs to the group of mixed odontogenic tumors. The descriptions of its clinical and radiological features in the literature are not always accurate and sometimes even contradictory. The aim of the present study was to critically evaluate their clinical and radiological features as reported in the English-language literature. A total of 114 well-documented cases of ameloblastic fibro-odontomas (103 from publications and 11 of our own new cases) were analyzed. The patients' age ranged from 8 months to 26 years (mean 9.6). There were 74 (65 %) males, with a male-to-female ratio of 1.85:1 (P = 0.001). The mandible was involved in 74 (65 %) cases, and the mandible-to-maxilla ratio was 1.85:1 (P < 0.001). Nearly 80 % of the lesions were located in the posterior region of the jaws, and most (58 %) were in the posterior mandible. Radiographically, most of the lesions were unilocular and only a few (~10 %) were multilocular. Most lesions were mixed radiolucent-radiopaque, and only a few (~5 %) were radiolucent. Almost all lesions (~92 %) were associated with the crown of an unerupted tooth/teeth. This comprehensive analysis of a large number of patients with an uncommon lesion revealed that ameloblastic fibro-odontomas are significantly more common in males and in the mandible, and that multilocular lesions are uncommon. It also revealed that, based on their clinical and radiological features, some of them are probably true neoplasms while others appear to be developing odontomas (hamartomas).

Unicystic ameloblastoma in an infant: a management dilemma.

The authors describe the conservative management of a rare case of unicystic ameloblastoma (mural subtype) in a 10-month-old girl, the youngest patient reported thus far in the literature. Rather than subject the infant to further surgery, it was decided to monitor her closely and perform an additional operation in the event of recurrence, thus enabling uninterrupted mandibular growth and tooth development. The patient is now 3.5 years old and periodic follow-up is ongoing, with no evidence of recurrence.

Is maspin immunolocalization a tool to differentiate central low-grade mucoepidermoid carcinoma from glandular odontogenic cyst?

Mucoepidermoid carcinoma (MEC) of the salivary glands has a low-grade variant (LGMEC), which may be found within the jawbones. LGMEC shares a number of histopathological similarities with glandular odontogenic cysts (GOC) of the jawbones. Maspin has been identified in several benign and malignant salivary gland neoplasms. We investigated the immunolocalization of maspin in LGMEC and GOC and evaluated its potential to distinguish between these two entities. Cases of LGMEC (n=6), GOC (n=8) and various odontogenic cysts with marked mucous metaplasia (OCMM, n=7), which served as controls, were immunohistochemically labeled for the binding of an antibody directed against maspin. Immunomorphometry was performed separately for maspin-immunopositive epithelial cells and epithelial-mucous cells in either their nuclear or cytoplasmic compartments. Results were presented as the volume fraction (Vv) of each element. The Vv of the maspin-immunopositive epithelial-mucous cytoplasm and nuclei was significantly higher in LGMEC than in GOC and OCMM (p<0.001 and p=0.026, respectively). In the epithelial cells, no significant differences were observed among the lesions (p>0.05). It is suggested that the high levels of maspin in the epithelial-mucous cells (in both cytoplasm and nuclei) in LGMEC may serve as a tool to distinguish it from GOC. This may be useful especially in equivocal cases and in small incisional biopsy samples.

Congenital granular cell epulis presents an immunohistochemical profile that distinguishes it from the granular cell tumor of the adult.

Congenital granular cell epulis (CGCE), a rare benign lesion arising from the mucosa of the alveolar ridges of the jaws in newborns, has a clinical course characterized by lack of further growth after birth. Histomorphologically, it resembles a granular cell tumor (GCT) of the adult. The histogenesis of this lesion is unclear. We submitted a series of five CGCEs to a large panel of antibodies in order to trace the origin of the constituent granular cells. The resultant immunohistochemical profile showed positivity of these cells to vimentin, NKI/C3, and PGP9.5. This does not confirm any particular cell type for the histogenetic origin of CGCE but may rather reflect a local metabolic or reactive change, providing supporting evidence that the lesion is of a non-neoplastic nature. In addition, the granular cells were non-reactive for S-100, NGFR/p75, and inhibin-alpha, which further contributes to the distinction between a CGCE and the adult GCT.

Central giant cell granuloma of the jawbones--new insights into molecular biology with clinical implications on treatment approaches.

Central giant cell granulomas (CGCG) constitute about 10% of benign jawbone lesions. Approximately one-third of CGCG exhibit local aggressive behavior with bone destruction and a tendency to recur. Cure of patients with aggressive CGCG can be achieved by en bloc resection with clear margins at the possible cost of esthetic, functional and psychological problems, mainly in young patients. It is in these cases where pharmacologic agents are most needed as an alternative treatment approach. Until now, pharmacologic agents for CGCG have been used empirically and, in a small number of cases, with various degrees of success. The purpose of this review is to present the recent findings on the phenotypic profile of the constituent cells in CGCG at the molecular level and discuss the inter-relations among them; to analyze the osteolytic potential concealed in the lesional cells; to provide an evidence-based rationale for the use of pharmacologic agents, and, consequently, to suggest a revised approach for their use.

Stromal myofibroblasts in central giant cell granuloma of the jaws cannot distinguish between non-aggressive and aggressive lesions.

OBJECTIVE: To investigate correlations between myofibroblast density (MFD) and biological behavior of a large series of non-aggressive and aggressive central giant cell granuloma lesions (CGCGs). METHODS: Twenty-four non-aggressive and 17 aggressive lesions were immunohistochemically stained with alpha smooth muscle actin. MFD was assessed using the point counting method in the lesions' core tissue and in control areas that consisted of non-involved, connective tissue surrounding the lesion. RESULTS: All CGCGs contained myofibroblasts among the stromal cells. No significant differences were found in the mean percentage of MFD (%MFD) of non-aggressive (20.8 +/- 15.7%) and aggressive (23.7 +/- 22.9%) lesions (P > 0.05) or in the mean %MFD of the respective control areas (1.4 +/- 2.2% and 1.7 +/- 4.1%; P > 0.05). The mean core tissue %MFD of both lesion types was significantly higher than that of the control areas (P < 0.001). CONCLUSION: Myofibroblasts were an integral component of CGCG stromal cells, but their density could not distinguish between non-aggressive and aggressive lesions.

Calcitonin nasal spray for treatment of central giant cell granuloma: clinical, radiological, and histological findings and immunohistochemical expression of calcitonin and glucocorticoid receptors.

OBJECTIVE: To provide clinical, radiological, and histopathologic analyses of 5 patients with central giant cell granuloma (CGCG) treated with calcitonin nasal spray; to compare the results to 11 well-documented cases in the literature; and to evaluate lesions for immunohistochemical expression of calcitonin receptors (CTR) and glucocorticoid receptors (GCR). STUDY DESIGN: Five patients with CGCG were treated with calcitonin nasal spray, 200 to 400 IU/day, for 13 to 64 months. CTR and GCR expression were examined at different treatment times. RESULTS: No lesions showed significant clinical and/or radiological improvement in size. The main benefit was thickening of the cortical plates. All patients eventually underwent curettage and continued calcitonin treatment. Significant radiological improvement was noticed 2 to 4 months postsurgical procedure. Each lesion exhibited a different immunoprofile for CTR and GCR, pretreatment and during treatment. CTR disappeared after long-term calcitonin treatment. GCR exhibited variable changes. CONCLUSION: Long-term nasal spray calcitonin was ineffective for CGCG management compared with calcitonin injections. It is suggested that lesions with an undesirable response should be evaluated for CTR and GCR expression at different treatment times for maximal benefit of calcitonin treatment.

Central (intraosseous) myofibroma of the mandible: clinical, radiologic, and histopathologic features of a rare lesion.

OBJECTIVE: Myofibroma frequently manifests as a solitary soft tissue tumor and less as simultaneous multiple tumors in both soft tissues and bones. The present study evaluated clinical, radiological, and histopathologic features of myofibroma of the jaws. STUDY DESIGN: Nineteen cases from the literature and 4 new cases were analyzed. RESULTS: At initial diagnosis, age ranged from birth to 34 years (mean 7.2 years, median 6 years). Male/female ratio was 2.3:1. Myofibromas were radiolucent solitary lesions located solely in the mandible: 70% unilocular, 30% multilocular; 67% with well-defined borders. Conservative treatment was performed on 75% of the patients; 25% underwent partial jaw resection. Where information was provided, no lesion recurred during 6-month to 17-year follow-up. CONCLUSION: Although rare, myofibroma of the mandible should be considered in the differential diagnosis of radiolucent lesions (particularly unilocular), especially in children. Treatment of choice is conservative surgery to minimize potential functional and/or esthetic damage.

Relative frequency of peripheral odontogenic tumors: a study of 45 new cases and comparison with studies from the literature.

BACKGROUND: Peripheral (extraosseous) odontogenic tumors are rare, and reports in the literature have mainly been single case reports or a small series of cases. The aim of this study was to determine the relative frequency of peripheral (extraosseous) odontogenic tumors relative to one another and relative to their central (intraosseous) counterparts in an oral pathology biopsy service and to compare these data with information available in the literature. METHODS: The files of the Pacific Oral and Maxillofacial Pathology Laboratory of the University of the Pacific, San Francisco, CA, USA, served as the source of material for this study. Files were systematically searched for all cases of peripheral odontogenic tumors (POTs) during a 20-year-period. RESULTS: There were 91,178 cases accessed in which central and POTs were identified in 1,133 (1.24%), central tumors in 1,088 (1.2%), and peripheral tumors in 45 (0.05%). Peripheral tumors accounted for 4% of all 1133 central and POTs. Peripheral odontogenic fibroma (PODF) was the most common of the 45 POTs accounting for 51.1% (23 cases) followed by peripheral ameloblastoma (PA) 28.9% (13 cases) and peripheral calcifying cystic odontogenic tumor (PCCOT) 13.3% (six cases). Peripheral calcifying epithelial odontogenic tumor, peripheral ameloblastic fibroma, and peripheral ameloblastic carcinoma were also identified--each comprised 2.2% (one case each). PODF was more common than its central counterpart by a 1.4:1 ratio. This was the only peripheral tumor that was more common than its central counterpart. PA accounted for 9.3% of all ameloblastomas and PCCOT for 26% of all calcifying cystic odontogenic tumors. CONCLUSION: There is only scarce information in the literature on the relative frequency of POTs. Additional studies should be conducted to determine the true relative frequency. To ensure accuracy, pathologists with experience in the field of odontogenic tumors should conduct these studies. Intraosseous tumors that perforate through the bone to the gingival tissue, clinically presenting as 'peripheral tumors' should be excluded.

Relative frequency of central odontogenic tumors: a study of 1,088 cases from Northern California and comparison to studies from other parts of the world.

PURPOSE: To determine the relative frequency of central odontogenic tumors in relation to all biopsy specimens and to one another in an oral pathology biopsy service and to compare the data with previous studies from different parts of the world. METHODS: Files from the Pacific Oral Pathology Laboratory of the University of the Pacific, San Francisco, CA served as a source of material for this study. Files were systematically searched for all cases of central (intraosseous) odontogenic tumors during a 20-year period. RESULTS: Central odontogenic tumors were identified in 1,088 (1.2%) cases out of the 91,178 accessed. Individually, of all odontogenic tumors, 75.9% were odontomas. The prevalence of the remaining tumors appears to be a rare occurrence. The second most common was ameloblastoma (11.7%), followed by odontogenic myxoma (2.2%). Odontomas are considered hamartomas or developmental anomalies. When excluded from the list of individual odontogenic tumors, ameloblastoma is the most common (48.5%), followed by odontogenic myxoma (9.2%), adenomatoid odontogenic tumor (7.3%), ameloblastic fibro-odontoma (7.3%), ameloblastic fibroma (6.5%), calcifying odontogenic cyst (6.5%), and odontogenic fibroma (6.1%). Each remaining tumor comprises less than 4%. CONCLUSIONS: Studies related to the relative frequency of individual odontogenic tumors from different parts of the world are difficult to compare because most studies are outdated, the list of tumors is limited, and new entities are not included. To determine the real relative frequency, further studies should be conducted, especially in Western societies, by experienced pathologists in the field of odontogenic tumors.

A comparative study of age-related changes between palatal and labial salivary glands.

OBJECTIVES: The purpose of this article was to compare age-related histomorphometric changes between palatal and labial salivary glands (PSG and LSG, respectively). STUDY DESIGN: Analysis of the mean proportional volume (MPV) of the acinar component (AC), ductal component (DC) and of the inflammatory component (IC) was performed on 120 samples of PSG and LSG obtained from subjects with no known history of salivary gland tumors/diseases. Samples were divided into young (n=30, < or =30y), adult (n=45, 31-60y) and old (n=45, >60y) age groups. RESULTS: In PSG, a significant decrease in MPV of AC (p<0.0001) with a concomitant significant increase in MPV of DC (p<0.0001) was found among all age groups. In LSG, a significant decrease in MPV of AC (p=0.002) with a concomitant increase in MPV of DC (p=0.002) was found between the adult and old age groups. A significant increase in MPV of IC in PSG was found between the young and adult groups (p<0.0001), while in LSG it became evident only between the adult and old groups (p<0.0001). Inflammatory and ductal components demonstrated the same pattern of age-related changes in both PSG and LSG. CONCLUSIONS: In light of these results, it is suggested that earlier and continuous changes in PSG, as compared to LSG, may partially explain the more frequent involvement of PSG in pathologic conditions.