A brief review of cytology in dentistry

Oral cytology is a non-invasive adjunctive diagnostic tool with a number of potential applications in the practice of dentistry. This brief review begins with a history of cytology in medicine and how cytology was initially applied in oral medicine. A description of the different technical aspects of oral cytology is provided, including the collection and processing of oral cytological samples, and the microscopic interpretation and reporting, along with their advantages and limitations. Applications for oral cytology are listed with a focus on the triage of patients presenting with oral potentially malignant disorders and oral mucosal infections. Furthermore, the utility of oral cytology roles across both expert (for example, secondary oral medicine or tertiary head and neck oncology services) and non-expert (for example, primary care general dental practice) clinical settings is explored. A detailed section covers the evidence-base for oral cytology as a diagnostic adjunctive technique in both the early detection and monitoring of patients with oral cancer and oral epithelial dysplasia. The review concludes with an exploration of future directions, including the integration of artificial intelligence for automated analysis and point of care 'smart diagnostics', thereby offering some insight into future opportunities for a wider application of oral cytology in dentistry.

Can precancerous stem cells be risk markers for malignant transformation in the oral mucosa?

Accurate assessment of the carcinogenic potential of oral mucosal diseases can significantly reduce the prevalence of oral cancer. We speculate that precancerous stem cells (pCSCs) arise during the evolution of carcinomas based on long-term experimental findings, published literature, and the cancer stem cell (CSC) theory, wherein pCSCs exist in precancerous lesions and have characteristics of both CSCs and normal stem cells. This apparently contradictory feature may be the foundation of the reversible transformation of precancerous lesions. Predicting malignant transformation in potentially malignant oral illnesses would allow for focused treatment, prognosis, and secondary prevention. Currently available clinical assays for chromosomal instability and DNA aneuploidy have several deficiencies. We hope that our study will increase attention to pCSC research and lead to the development of novel strategies for the prevention and treatment of oral cancer by identifying pCSC markers.

Impact of Chromosome 9 Numerical Imbalances in Oral Squamous Cell Carcinoma: A Pilot Grid-Based Centromere Analysis

Oral squamous cell carcinoma (OSCC) is considered an aggressive malignancy, mainly due to its increased propensity to provide local and distant lymph node metastases. Gross chromosome instability (CI; polysomy/aneuploidy/monosomy), combined or not with specific gene alterations, is implicated in the development and progression of solid malignancies, including OSCC. In order to further study the relationship between these genetic alterations and the aggressive biological behavior of OSCCs, we investigated the frequency and impact of chromosome 9 numerical imbalances in these tumors. Fifty (n = 50) formalin-fixed, paraffin-embedded primary OSCC tissue sections were used. Chromogenic in situ hybridization (CISH) was implemented for detecting chromosome 9 (CEN-centromere enumeration) numerical alterations. Concerning the screening process in CISH slides, a novel, real-time reference and calibration grid platform was implemented. Chromosome 9 polysomy was observed in 8/50 (16%) tissue sections, whereas the rest of them demonstrated a normal, diploid pattern (42/50; 84%). Chromosome 9 polysomy was associated with the grade of differentiation of the examined tumors (p = 0.036). Chromosome 9 numerical imbalances (polysomy) were observed in sub-groups of OSCCs correlating with a progressive dedifferentiation of the malignant tissues. Concerning the implementation of the proposed grid-based platform as described above on CISH slides, it provides a novel, fast, and accurate screening mapping mechanism for detecting chromosome numerical imbalances.

Topical application of morphine for wound healing and analgesia in patients with oral lichen planus: a randomized, double-blind, placebo-controlled study

OBJECTIVE

The objective of this study was to investigate the effect of topical morphine on erosive/ulcerative lesions in patients with oral lichen planus (OLP). Previous studies reported on an enhanced remission of skin wounds when morphine was applied topically.

MATERIALS AND METHODS

This was single-center, prospective, double-blind, placebo-controlled, randomized, multi-arm (3), phase II study (RCT). Patients diagnosed with erosive and/or ulcerative OLP applied 0.2 or 0.4 mg morphine dissolved in glycerine, three times a day for 5 days. The primary outcome was the extent of healing. Secondary outcomes were as follows: (1) effect on pain, (2) presence and severity of opioid-related central and local side effects, (3) whether patients required 'rescue medication' for treatment of pain, and (4) total intake of test substance.

RESULTS

A total of 123 patients were screened for eligibility, 45 patients were recruited into the study, and 43 completed it. Patients applied a solution of either placebo or 0.2 or 0.4% morphine in groups of n = 12, n = 15, and n = 16, respectively. Extent of healing was similar in the three groups. Severity of pain was minor pre-treatment and throughout the course of the study. Only minor adverse events were reported (dry mouth, burning sensation).

CONCLUSION

Morphine did not enhance wound healing compared to placebo-treated patients. Healing was observed in all groups, which may be attributed to an effect of glycerine or to the natural course of the disease. Patients experienced only mild levels of pain, rendering the model insensitive for assessing pain.

CLINICAL RELEVANCE

OLP is a chronic disease and current treatment options are limited. Healing occurred in all three study groups, an effect we attribute to the carrier.

Image-based DNA ploidy analysis aids prediction of malignant transformation in oral lichen planus

OBJECTIVES

To investigate the potential of image-based DNA ploidy analysis to predict malignant transformation in patients with oral lichen planus (OLP).

STUDY DESIGN

DNA ploidy analysis was performed on biopsy samples from 14 patients with OLP who underwent malignant transformation. As controls, 42 OLP lesions showing unusual clinical features suggesting a transformation risk and 68 samples of clinically and histologically typical OLP were included. Cases with dysplasia on initial biopsy were excluded. Eighty fibroepithelial polyps acted as methodologic controls. Epithelial nuclei were isolated from formalin-fixed paraffin embedded biopsy samples and monolayers stained with Feulgen for automated image cytometry to establish DNA content. Ploidy status was correlated to outcome using Kaplan-Meier analysis and log-rank Mantel-Cox tests.

RESULTS

All controls and typical OLP were diploid and none underwent malignant transformation in mean follow-up of 14 years (10-18 years). One unusual OLP developed carcinoma and all were diploid. The 14 patients with transformation developed 21 carcinomas. In the 11 patients who had a prior biopsy, 4 were aneuploid.

CONCLUSIONS

DNA ploidy analysis predicted malignant transformation in more than one third (36.4%) of patients with OLP with a preceding biopsy (n = 11). This premalignant nature could not have been diagnosed clinically or by histologic dysplasia assessment.

Association of CD24 and the adenomatous polyposis coli gene polymorphisms with oral lichen planus

OBJECTIVE

CD24 and the adenomatous polyposis coli (APC) gene polymorphisms are known to predispose to malignant disease. We aimed to investigate their association with risk and susceptibility of oral lichen planus (OLP) in an Israeli Jewish population.

STUDY DESIGN

The study included 54 patients, of which 41 were females (75.9%) and 13 males (24.1%); of the 533 controls, 224 were females (42.0%) and 309 males (57.9%). Genotyping was performed. Two APC (I1307 K, E1317 Q) and four CD24 variants--C170 T (rs52812045), TG1527 del (rs3838646), A1626 G (rs1058881), and A1056 G (rs1058818)--were assessed. Frequencies were analyzed using the Chi-square test. Two-sided P < .05 values were considered significant. Odds ratios and 95% confidence intervals were obtained by logistic regression analyses.

RESULTS

CD24 A1056 G carriers have a significantly lower risk of OLP compared with individuals with the wild-type variant (P = .001). A significantly lower risk was found for heterozygote (P = .008) and homozygote carriers (P = .002). Homozygote CD24 A1626 G carriers had a significant higher risk for OLP compared with nonhomozygote carriers (P = .040). CD24 C170 T, TG1527 del, and APC polymorphisms did not show significant associations with OLP risk.

CONCLUSIONS

CD24 A1626 G is more frequent in OLP patients, contributes to disease risk, and could play a role in OLP susceptibility. A significant association between CD24 A1056 G and a lower OLP incidence was found, suggesting that it may confer protection against OLP risk and progression.

Epigenetic Modifications and Accumulation of DNA Double-Strand Breaks in Oral Lichen Planus Lesions Presenting Poor Response to Therapy

Epigenetics refers to changes in cell characteristics that occur independently of modifications to the deoxyribonucleic acid (DNA) sequence. Alterations mediated by epigenetic mechanisms are important factors in cancer progression. Although an exciting prospect, the identification of early epigenetic markers associated with clinical outcome in premalignant and malignant disorders remains elusive. We examined alterations in chromatin acetylation in oral lichen planus (OLP) with distinct clinical behavior and compared the alterations to the levels of DNA double-strand breaks (DSBs). We analyzed 42 OLP patients, who had different responses to therapy, for acetyl-histone H3 at lys9 (H3K9ac), which is associated with enhanced transcription and nuclear decondensation, and the presence of DSBs, as determined by accumulation of phosphorylated γH2AX foci. Patients with high levels of H3K9ac acetylation failed to respond to therapy or experienced disease recurrence shortly after therapy. Similar to H3K9ac, patients who responded poorly to therapy had increased accumulation of DNA DSB, indicating genomic instability. These findings suggest that histone modifications occur in OLP, and H3K9ac and γH2AX histones may serve as epigenetic markers for OLP recurrence.

The dynamics of oral lichen planus: a retrospective clinicopathological study

To evaluate disease dynamics, treatment results, and frequency of malignant transformation. Ten-year single center retrospective study. The study included 171 patients, 28-99 years old. Follow-up was 1-16 years. 49.5% exhibited changes in clinical presentation, with 19% yearly increase of probability for type shift. Index of extent (number of oral locations) showed a mean 40% decrease and 94.1% reported improvement. There were significant differences between treated and untreated patients (P=0.012). Patients with or without systemic diseases had identical treatment requirements for oral lesions. The prevalence of SCC was 5.8%. Oral lichen planus constantly changes presentation and extent of involvement. The effect of systemic diseases was insignificant in the present study. There is a clear value for treatment to reduce the extent of lesions. The results indicate that all clinical forms of the disease need to be equally followed since the clinical presentation typically changes over time, while malignant transformation can occur in all forms.

Oral lichen planus and malignant transformation: a longitudinal cohort study

OBJECTIVE

Oral lichen planus (OLP) is associated with risk for developing oral squamous cell carcinoma (OSCC). We performed a 7-year prospective study to assess the incidence of malignant transformation of OLP among adults.

STUDY DESIGN

Three hundred twenty-seven OLP patients, 229 women (70.0%) and 98 men (30.0%), were observed during the follow-up period.

RESULTS

During a mean follow-up of 81.7 months, 8 of 327 patients developed an OSCC in OLP areas (0.36%/y), yielding the high overall standardized incidence ratio of 17.7 (95% confidence interval [CI] 8.8-35.3). The standardized incidence ratio for OSCC was significantly higher in women [27.0 (95% CI 11.2-64.8)] than in men [11.2 (95% CI 3.6-34.9)]. Six OSCCs were well differentiated (75%) and 2 moderately differentiated (25%). Three subjects (37.5%) developed recurrences within 2 years (mean 16.1 ± 3.5 months). Disease-free survival rate after 69.8 months was 97.3%.

CONCLUSIONS

OLP was associated with a significant increase in the risk for OSCC. Close surveillance may help to reduce the morbidity of OSCC arising from OLP at 24 months.

Chromosomal numerical aberrations in apparently normal oral mucosa of heavy smokers affected by lung cancer

Cigarette smoke creates a field of injury in the epithelial lining of the entire respiratory tract causing an increased risk for the development of malignant lesions. It is conceivable, therefore, that early genetic alterations, can be detected in oral mucosa of heavy smokers mainly those affected by lung cancer. As aneuploidy was shown to be an early event in oral carcinogenesis, we aimed to investigate the prevalence of aneuploid cells (ACs) in samples obtained from apparently normal looking oral mucosa of heavy smokers affected by lung cancer (LC). Two brush samples were collected from the oral mucosa of 152 subjects; 31 heavy smokers with LC, 59 heavy smokers without LC and 62 never-smokers. The samples were simultaneously analyzed for morphology and fluorescent in situ hybridization (FISH) using chromosomes 2 and 8 centromeric probes. Over 2% ACs were found in 23% of heavy smokers with LC compared to 12% in heavy smokers without LC and 5% of the never-smokers group (P=0.015). A trend was also noticed when comparing the group of heavy smokers without LC with the never-smokers (P=0.198). We conclude that heavy smokers harbour detectable chromosomal numerical aberrations in oral epithelial cells of normal looking mucosa. These aberrations are more frequently found in heavy smokers affected by LC.