Résumé
Abstract This study aimed to analyze the molecular characteristics of oral epithelial dysplasia (OED), highlighting the pathways and variants of genes that are frequently mutated in oral squamous cell carcinoma (OSCC) and other cancers. Ten archival OED cases were retrieved for retrospective clinicopathological analysis and exome sequencing. Comparative genomic analysis was performed between high-grade dysplasia (HGD) and low-grade dysplasia (LGD), focusing on 57 well-known cancer genes, of which 10 were previously described as the most mutated in OSCC. HGD cases had significantly more variants; however, a similar mutational landscape to OSCC was observed in both groups. CASP8+FAT1/HRAS, TP53, and miscellaneous molecular signatures were also present. FAT1 is the gene that is most affected by pathogenic variants. Hierarchical divisive clustering showed division between the two groups: "HGD-like cluster" with 4HGD and 2LGD and "LGD-like cluster" with 4 LGD. MLL4 pathogenic variants were exclusively in the "LGD-like cluster". TP53 was affected in one case of HGD; however, its pathway was usually altered. We describe new insights into the genetic basis of epithelial malignant transformation by genomic analysis, highlighting those associated with FAT1 and TP53. Some LGDs presented a similar mutational landscape to HGD after cluster analysis. Perhaps molecular alterations have not yet been reflected in histomorphology. The relative risk of malignant transformation in this molecular subgroup should be addressed in future studies.
Résumé
Background: Oral cancer in Chile corresponds approximately to 1.6% of all cancer cases. There are few studies about oral epithelial dysplasia and oral squamous cell carcinoma in the Chilean population. Aim: To determine the frequency of hyperkeratosis, mild, moderate and severe oral epithelial dysplasia, in situ carcinoma and squamous cell carcinoma of the oral and oropharyngeal mucosa in a registry of the Oral Pathology Reference Institute of the Faculty of Dentistry, Universidad de Chile, in a ten years period. Material and Methods: Review of clinical records and pathological plates of 389 patients, obtained between 1990 and 2009. Cases were selected according to their pathological diagnosis, including hyperkeratosis, oral epithelial dysplasia, in situ carcinoma, squamous cell carcinoma and verrucous carcinoma. Results: Forty four percent of cases were squamous cell carcinoma, followed by hyperkeratosis in 37% and mild epithelial dysplasia in 11%. Squamous cell carcinoma was more common in men aged over 50 years. Most of the potentially malignant disorders presented clinically as leukoplakia and squamous cell carcinoma were clinically recognized as cancer. Conclusions: In this study, men aged over 50 years are the highest risk group for oral cancer. Early diagnosis is deficient since most of these lesions were diagnosed when squamous cell carcinoma became invasive. Leukoplakia diagnosis is mostly associated with hyperkeratosis and epithelial dysplasia, therefore biopsy of these lesions is mandatory to improve early diagnosis.