Adenoid cystic carcinoma of the retromolar pad region: A case report.

INTRODUCTION: Adenoid cystic carcinoma (ACC) is one of the most common salivary gland malignancies, mostly occurs in the major and minor salivary glands in the oral and maxillofacial region. The development of ACC in the retromolar pad is extremely rare, which limits establishing proper diagnosis and management. PRESENTATION OF CASE: A patient described a 2-month history of finding a mass behind the lower left posterior teeth. Based on the physical examination and radiographic findings, we got an initial impression of a benign mucocele, the nature of which was to be investigated further. Pathological examination of the resected tissue resulted in a diagnosis of ACC. Follow-up visits showed no recurrence during the subsequent 54 months. DISCUSSION: In cases with an uncertain diagnosis based on medical history, clinical features and imaging examinations, it is important to proceed carefully with the possibility of a tumor in mind. CONCLUSION: ACC in the retromolar pad is rare and can be easily misdiagnosed. Clinical, radiographic, and pathological evidence confirm a definitive diagnosis. Long-term follow-up is important for the full analysis of ACC treatment.

PTCH/SMO gene mutations in odontogenic keratocysts and drug interventions.

BACKGROUND: Odontogenic keratocysts (OKCs) are odontogenic jaw lesions that cause destruction and dysfunction of the jawbone. OKCs can be sporadic or associated with nevoid basic cell carcinoma syndrome (NBCCS). However, the factors that initiate OKCs and the mechanism of cyst formation remain unclear. Here, we investigated the impact of PTCH1 and SMO mutations on disease progression, as well as the effects of sonic hedgehog (SHH) signaling pathway inhibitors GDC-0449 and GANT61 on OKC fibroblasts. METHODS: Eight sporadic OKC fibroblasts without gene mutations were used as the control, and six NBCCS-related fibroblasts were cultured in vitro. The effect of PTCH1 non-truncated mutation 3499G>A (p.G1167R) and SMO c.2081C>G (p.P694R) mutation on OKC fibroblast proliferation was examined by EdU assay. CCK8 and wound-healing assays detected the effects of OKC fibroblasts carrying PTCH1 c.3499G>A (p.G1167R) and SMO c.2081C>G (p.P694R) mutations on the proliferation and migration of HaCaT cells after co-culture. Quantitative real-time PCR detected the effects of GDC-0449 or GANT61 on the SHH signaling pathway in NBCCS-related OKCs with PTCH1 truncated mutations and PTCH1 c.3499G>A (p.G1167R) and/or SMO c.2081C>G (p.P694R) mutations. RESULTS: PTCH1 c.3499G>A (p.G1167R) and SMO c.2081C>G (p.P694R) promoted the proliferation of OKC fibroblasts. The proliferation and migration of HaCaT cells were affected by NBCCS-related OKC fibroblasts carrying PTCH1 c.3499G>A (p.G1167R) and SMO c.2081C>G (p.P694R) mutations. GDC-0449 significantly inhibited the SHH signaling pathway in NBCCS-related OKC fibroblasts with PTCH1 truncated mutations. An NBCCS-related OKC carrying PTCH1 c.3499G>A (p.G1167R) and SMO c.2081C>G (p.P694R) mutations were resistant to GDC-0449 but inhibited by GANT61. CONCLUSIONS: Genetic mutations in OKC fibroblasts may affect the biological behavior of epithelial and stromal cells and cause disease. GDC-0449 could be used to treat OKCs, especially NBCCS-related OKCs with PTCH1 truncated mutations. SMO c.2081C>G (p.P694R) may lead to resistance to GDC-0449; however, GANT61 may be used as an alternative inhibitor.

Application of the presentation-assimilation-discussion class in oral pathology teaching.

OBJECTIVES: The presentation-assimilation-discussion (PAD) class is a novel teaching method in which half the class time is allocated for the instructor's presentation and the other half for student's assimilation and discussion. This study evaluates and compares the teaching outcomes of the PAD class and traditional lecture-based method in oral pathology courses in School of Stomatology, Kunming Medical University. MATERIALS AND METHODS: The experimental and control groups included 88 undergraduates from Class 2017 and 72 undergraduates from Class 2016, respectively. The PAD method was applied on the experimental group in 2019, whereas the traditional lecture-based method was applied on the control group in 2018. The two groups' teaching outcomes were compared using final theory tests, biopsy diagnostic tests, and questionnaires. The Mann-Whitney U-test and independent-sample t-test were adopted for statistical analysis. RESULTS: In five multiple-choice questions examining the same knowledge point from final theory tests, the distribution of the final scores showed a statistically significant difference between the two groups (p < 0.05). In the biopsy diagnostic tests, the experimental group scored higher than the control group (p < 0.05). In the questionnaires, there was no statistically significant difference for the "enhancing knowledge mastery" item (p > 0.05). However, the experimental group showed significant superiority in the remaining nine items (p < 0.05). [Correction added on August 30, 2021, after first online publication: The data value p was corrected in the last sentence of result section.] CONCLUSIONS: Compared with the traditional lecture-based teaching, the PAD class stimulated a passion for learning among students and results in improved teaching outcomes. Therefore, the application of PAD class in oral pathology teaching should be recommended.

PTCH1 alterations are frequent but other genetic alterations are rare in sporadic odontogenic keratocysts.

OBJECTIVE: Odontogenic keratocysts (OKCs) are benign jaw lesions with high growth potential and propensity for recurrence. Our previous study revealed that PTCH1 mutations, which were frequently detected in sporadic OKCs, might be underestimated due to the masking effect of the stromal components within the tested tissues. We aimed to confirm these results in larger scale and further present the unbiased view of the genomic basis of sporadic OKCs except PTCH1. MATERIALS AND METHODS: We analyzed PTCH1 mutations in additional 19 samples. Using whole-exome sequencing (WES), we further characterized the mutational landscape of five sporadic OKC samples lacking PTCH1 mutation and loss of heterozygosity (LOH). RESULTS: Combined with our previously reported 19 cases, thirty of 38 (79%) cases harbored PTCH1 mutations. Through whole-exome sequencing and integrative analysis, 22 novel mutations were confirmed among five PTCH1-negative samples. No recurrent mutations were identified in the WES samples and validation cohort of 10 OKCs. CONCLUSIONS: Our data further confirmed the frequent PTCH1 mutation and other rare genetic alterations in sporadic OKCs, highlighting the central role of SHH signaling pathway. In PTCH1-negative cases, other rare mutations scattered in a subset of OKCs were independent of the SHH pathway. These results suggested that an SHH inhibitor may be effective to treat the majority of OKCs.

Effect of the sonic hedgehog inhibitor GDC-0449 on an in vitro isogenic cellular model simulating odontogenic keratocysts.

Odontogenic keratocysts (OKCs) are common cystic lesions of odontogenic epithelial origin that can occur sporadically or in association with naevoid basal cell carcinoma syndrome (NBCCS). OKCs are locally aggressive, cause marked destruction of the jaw bones and have a propensity to recur. PTCH1 mutations (at ∼80%) are frequently detected in the epithelia of both NBCCS-related and sporadic OKCs, suggesting that PTCH1 inactivation might constitutively activate sonic hedgehog (SHH) signalling and play a major role in disease pathogenesis. Thus, small molecule inhibitors of SHH signalling might represent a new treatment strategy for OKCs. However, studies on the molecular mechanisms associated with OKCs have been hampered by limited epithelial cell yields during OKC explant culture. Here, we constructed an isogenic PTCH1R135X/+ cellular model of PTCH1 inactivation by introducing a heterozygous mutation, namely, c.403C>T (p.R135X), which has been identified in OKC patients, into a human embryonic stem cell line using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system. This was followed by the induction of epithelial differentiation. Using this in vitro isogenic cellular model, we verified that the PTCH1R135X/+ heterozygous mutation causes ligand-independent activation of SHH signalling due to PTCH1 haploinsufficiency. This activation was found to be downregulated in a dose-dependent manner by the SHH pathway inhibitor GDC-0449. In addition, through inhibition of activated SHH signalling, the enhanced proliferation observed in these induced cells was suppressed, suggesting that GDC-0449 might represent an effective inhibitor of the SHH pathway for use during OKC treatment.

Heterozygous PTCH1 Mutations Impact the Bone Metabolism in Patients With Nevoid Basal Cell Carcinoma Syndrome Likely by Regulating SPARC Expression.

Nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by bone and skin abnormalities and a predisposition to various tumors. Keratocystic odontogenic tumors (KCOTs), which are common tumors of the jaw that cause extensive damage to the jawbone, are usually accompanied with NBCCS. Germline PTCH1 mutations in NBCCS tumorigenesis have been frequently studied; however, little is known regarding the pathogenesis of bone abnormalities in this disease. This study sought to investigate the mechanism underlying heterozygous PTCH1 mutation-mediated abnormal bone metabolism in patients with NBCCS. Stromal cells were isolated from the fibrous capsules of patients with NBCCS-associated or non-syndromic keratocystic odontogenic tumors and non-syndromic tumor stromal cells without PTCH1 mutations served as controls. Germline PTCH1 heterozygous mutations were confirmed in all NBCCS samples and differential protein expression was identified using tandem mass tag-labeled proteomics analysis. Our findings revealed that osteonectin/SPARC expression was significantly downregulated in syndromic stromal cells compared with non-syndromic stromal cells. SPARC expression was even lower in stromal cells carrying PTCH1 protein truncation mutations. PTCH1 siRNA transfection demonstrated that SPARC downregulation correlates with decreased PTCH1 expression. Furthermore, exogenous SPARC promoted osteogenic differentiation of syndromic stromal cells with enhanced development of calcium nodules. In addition, bone mineral density tests showed that patients with NBCCS exhibit weak bone mass compared with sex- and age-matched controls. This study indicates that germline PTCH1 heterozygous mutations play a major role in bone metabolism in patients with NBCCS, in particular in those with PTCH1 protein truncation mutations. SPARC may represent an important downstream modulator of PTCH1 mediation of bone metabolism. Thus, bone mineral density monitoring is critical for patients with NBCCS for prevention of osteoporosis. In addition, surgical procedures on syndromic-associated KCOTs should be performed with consideration of the weaker bone mass in such patients. © 2016 American Society for Bone and Mineral Research.