Introduction
Tobacco, alcohol, and betel use are the primary risk factors for oral squamous cell carcinomas (OSCC), the majority of oral malignancies, as well as many other potentially malignant lesions (PML).1, 2 Early PML diagnosis is anticipated to lower mortality.3, 4 Prognosis can be improved and treatment can begin more quickly in cases of early OSCC diagnosis.5 Currently, the gold standard for identifying potentially malignant diseases (PMDs) and oral squamous cell carcinoma (OSCC) is routine oral examination (visual and tactile assessment of accessible oral structures) combined with tissue sampling. Nevertheless, there are several drawbacks to this approach as well, such as sample bias, which may lead to an incorrect or underdiagnosed diagnosis, particularly in the case of multifocal lesions.6 Hence, the search for noninvasive, quick, and affordable screening techniques with sufficient sensitivity and specificity for the early detection of oral cancer is urgently needed. Thus, the various diagnostic methods used to identify precancerous and cancerous lesions are as follows:
Conventional oral examination
Vital tissue staining
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Histopathological methods
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Molecular methods
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Optical techniques
Fluorescence spectroscopy
Vizilite
VELscope7
Other methods
Conventional Oral Examination
Under typical incandescent light, the oral cavity is the site of the customary examination. For a very long time, it has been the accepted procedure for screening for oral cancer. Although it works wonders for some skin conditions, there is still debate on its applicability to oral cancer screening.8, 9
Vital Tissue Staining
In addition to toluidine blue, acetic acid, methylene blue, and iodine have also been tried as staining techniques. Acidophilic dye toluidine blue, which belongs to the thiazine group, is used to stain acidic cell tissue elements like DNA and RNA. It attaches itself to DNA by stacking, aggregating, or intercalation. The quantity of DNA determines the degree of binding. Loss of cell cohesion, accelerated mitosis, more nucleic acids, and bigger intracellular channels that improve dye penetration are all thought to contribute to the uptake of dye by dysplastic lesions and carcinomas.10
Exfoliative Cytology
In order to exfoliate deeper cells as well as superficial cells, which are scraped off and examined under a microscope, epithelial cells beneath neoplasms must lose their cohesiveness, according to the fundamental principle of exfoliative cytology.11 Its non-invasiveness, speed, simplicity, and suitability for patients with systemic disorders are its advantages. Cytology is an addition to surgical biopsy, not a replacement for it.11, 12
Oral Brush Biopsy
A straightforward, non-invasive chairside procedure called brush biopsy takes a full thickness sample of the lesion. Until precise bleeding is clinically identified, the brush is applied to the lesion and rotated. After being collected, the cellular material is put on a slide, coated, dyed, and then examined using a computer.7
Liquid-Based Cytology
One of the newest advancements in screening technologies is liquid-based cytology. Using a brush-like tool, samples are gathered, dipped in a vial of liquid preservative, and then brought to the laboratory where they are cleared of any obscuring substances, mucus, and blood before being centrifuged using a standard centrifugation technique to extract the cells. After discarding the supernatant, the resulting film is combined with a cell base solution and placed onto a sanitized slide.13, 14
Fine Needle Aspiration Cytology
For oral squamous cell carcinoma, FNAC is a valid diagnostic tool; however, its applicability in cases of oral leukoplakia is restricted.15 Because both benign and malignant salivary gland neoplasms share overlapping morphologic characteristics, FNA in salivary gland lesions is one of the most challenging areas of cytopathology. Additionally, different histological patterns within the same tumor may reveal different characteristics.16
Biopsy and Histopathology
Biopsy and histological inspection continue to be the gold standard for cancer diagnosis, despite the abundance of supplements available.14, 17 While clinical supplements aid in lesion visualization, only histological testing can determine the extent, depth, and degree of the lesion. 7
Molecular Methods
Fluorescent in situ hybridization (FISH), chain reaction (PCR), microarray, flow cytometry, immunohistochemistry (IHC), tumour markers, and laser capture microdissection (LCM) are among the many molecular techniques that are available.18 These methods can be applied to immunophenotyping, chromosomal mapping, prognostic, genomic, and proteomic tumor marker validation, generation of new markers, biology diagnosis, cytogenetic cancer diagnosis, and DNA ploidy determination.7, 18 The accuracy and usefulness of diagnostic testing have increased with the use of the PCR method. The main issue is that it is still prone to amplification artifacts and contamination, which could make data interpretation more difficult.19 In situ hybridization (ISH) can be produced by combining molecular biology techniques with measures of gene expression in tissues and cells. In this manner, it is easy to identify specific cells using RNA and DNA.20
Fluorescence Spectroscopy
The apparent benefits of being able to diagnose disease without having to remove a tissue sample reduce patient trauma and have financial ramifications. Optical spectroscopy systems are valued for their ability to provide tissue diagnostics quickly, in real-time, non-invasively, and in situ.21, 22, 23 The three primary spectroscopic methods now employed to identify malignancies and oral dysplasia are fluorescence, Raman and elastic scattering (ESS).22 An emerging method called ESS produces a wavelength-dependent spectrum that shows morphological and structural changes in tissues. It provides information about the tissue's absorptive and scattering characteristics throughout a broad spectrum of wavelengths.7
Vizilite
Studies have demonstrated that Vizilite enhances conventional visual evaluation. At 430, 540, and 580 nm, a single-use, disposable chemiluminescent light stick emits light. This may be handled with one hand. Normal epithelium (EP) absorbs light and appears black, but hyperkeratinized or dysplastic tumors reflect light and appear white. 17 To detect oral cancer early, observe any changes with a chemiluminescent light (like Vizilite) and rinse with diluted acetic acid. 24
Velscope
It is a portable optical device that allows for direct observation of oral autofluorescence. Medical experts can now utilize it as a helpful diagnostic tool to identify oral sickness early on. It has recently been available. It has been beneficial in the detection and prevention of several cancers, including as those of the skin, cervix, lung, and oral cavity. The principal justification for employing tissue autofluorescence in the identification of dysplastic lesions within the oral cavity is based on the ways in which light modifies the structure and uptake of both the epithelium and the subepithelial stroma.25
Saliva-Based Oral Cancer Diagnostics
The use of saliva in the detection of OSCC is relatively new. Oral fluid, sometimes known as saliva, is a widely accessible, non-invasive, and highly useful diagnostic tool. There's a chance that saliva transcriptome-based diagnostics will be utilized in the future to identify oral cancer. 26 In addition to abnormally high levels of O6-methyl guanine-DNA methyltransferase, death-related protein kinase, and tumor suppressor gene (TSG) p16, patients with head and neck conditions also had abnormally high levels of Capnocytophaga gingivalis, Prevotella melaninogenica, and Streptococcus mitis in their saliva. However, there is currently insufficient data to back up the idea that sound could be a reliable diagnostic indicator.27
Dna Ploidy and Quantification of Nuclear DNA Content
The quantity of DNA copies in a cell's nucleus, or DNA ploidy, can be used as a stand-in for the degree of genetic damage. The separation of chromosomal segments or the unequal distribution of chromosomes among daughter cells during mitosis are the main causes of aneuploidy in many malignancies. DNA image cytometry is a sensitive method that doesn't require tissue biopsy for cancer detection. 28
Serum Profiling
In patients with oral cancer, serum profiling has revealed variations in the amounts of a few minerals, antigens, and immune complexes. According to a study, people with oral cancer had considerably lower levels of iron and selenium and greater amounts of copper. Its low diagnostic sensitivity and specificity raise doubts about its dependability as a diagnostic tool.29, 30
Di-electrophoresis
It can be utilized as a possible tool for the early identification of oral cancer because it is a non-invasive method to measure the conductivity, permittivity of cellular cytoplasm and membrane, and other electrophysiological characteristics.31
Molecular Imaging in Adjunct with Ct, Mri and Pet
When used in conjunction with CT, MRI, and PET scans, molecular imaging has the potential to improve cancer detection and staging by highlighting the distinct functional characteristics of cancerous cells. Molecular imaging applications have demonstrated in a number of recent investigations that they can reveal characteristics of carcinogenesis at much earlier stages.31
Identafi 3000
In conjunction with traditional anatomical imaging, this technique makes use of fluorescence, fiber optics, and confocal microscopy to precisely map and highlight the lesion in the screened region (Identafi 3000, Dental EZ, Malvern, PA, USA). Because it is small, it can easily reach every tissue in your mouth. Changes in angiogenesis can be observed by flashing a certain green-amber light on the tissue, much like a VELscope.32
Conclusion
The field of histopathology anticipates that diagnostic macroscopic and microscopic will advance in tandem with molecular pathology, not in opposition to it. With the primary goal of treating PMLs and OSCCS as soon as possible, it is clearer what function these cutting-edge, futuristic diagnostic clinical tools serve. Early detection can prevent the lesions from becoming cancerous, which can result in the early creation of treatment tailored to each patient. The importance of these state-of-the-art, forward-thinking diagnostic clinical techniques is further highlighted by the urgent need for early PML and OSCC identification and treatment.
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