|Year : 2014 | Volume
| Issue : 1 | Page : 10-16
Diagnosis of oral cancer: The past and present
G. Sridhar Reddy, K. Eswara Rao, K. Kiran Kumar, P. Chandra Sekhar, K. Lalith Prakash Chandra, B. Venkata Ramana Reddy
Department of Oral Pathology, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India
|Date of Web Publication||15-May-2014|
G. Sridhar Reddy
Department of Oral Pathology, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Oral cancer prevalence in Asia-pacific region is at an alarming stage due to the adverse habits and different socio-economic and cultural status of the population. The better understanding of the disease process at the molecular level has altered the approach of the oral cancer towards early diagnosis of the lesion rather than late stages to reduce the morbidity and mortality. A good number of screening techniques has been time tested for the sensitivity and specificity in diagnosing oral cancer in the initial premalignant stages. Surgical biopsy is a gold standard for diagnosis but this needs professional services, which are impractical at times. Alternative screening methods which are noninvasive, easily performed and highly accurate are the norms for any test to accept as an alternative for histopathology. This article focuses on some screening techniques, which are done either as confirmative or adjuvant for histopathology.
Keywords: Chair side oral screening techniques, cytology in oral cancer, screening techniques
|How to cite this article:|
Reddy GS, Rao KE, Kumar KK, Sekhar PC, Prakash Chandra KL, Ramana Reddy BV. Diagnosis of oral cancer: The past and present. J Orofac Sci 2014;6:10-6
|How to cite this URL:|
Reddy GS, Rao KE, Kumar KK, Sekhar PC, Prakash Chandra KL, Ramana Reddy BV. Diagnosis of oral cancer: The past and present. J Orofac Sci [serial online] 2014 [cited 2017 Mar 25];6:10-6. Available from: http://www.jofs.in/text.asp?2014/6/1/10/132565
| Introduction|| |
Oral cancer is the sixth most frequently occurring malignant tumor and is the major cause of morbidity and mortality with metastatic and invasive ability.  The incidence of oral cancer differs widely in various parts of the world with 2-10 per 100,000 population per year. High incidence of oral cancer is seen in South Asian countries like Srilanka, India, Pakistan, and Bangladesh. In India the incidence is 7-17/100,000 persons/year with 75,000-80,000 new cases registered annually.  Detecting oral cancer in its early stages dramatically affects survival rates compared with detecting it in later stages. Nevertheless, around 50% of diagnosed patients die within 5 years.  A number of established cancer screening programs have been shown to significantly reduce patient morbidity and mortality.  Regular check-ups, including an examination of the entire mouth, are essential in the early detection of cancerous and pre-cancerous conditions. Unfortunately, early detection of oral precancerous and cancerous lesions has proved difficult, as the lesions are asymptomatic, doctors' casual approach towards innocuous lesions and as well as the fact that 50% of patients have regional or distant metastases at time of diagnosis. 
With increased technological advances, the dental profession has developed an oral cancer screening device that aids in early detection. Screening for cancer involves looking for cancerous cells or pre-cancerous conditions before any symptoms are present and thereby help and prevent this deadly disease. An oral cancer screening device should be quick, easy and convenient.
In the not so distant days of the "one gene, one protein, one biomarker" paradigm, the pace of progress was relatively slow. Today the implementation of comprehensive modalities of analysis is taking at such speed that by the time novel strategies are validated and integrated into established patterns of medical practice, they may be obsolete. This circumstance calls for a codification and streamlining of the validation pathways to facilitate the organization of large-scale cooperative studies designed to validate new diagnostic tools. The establishment standards and common protocols to cleanse, report and analyze data will be of critical importance in the dissemination of new technologies.
A Conventional Oral Examination (COE), using normal (incandescent) light, has long been the standard method for oral cancer screening. The National Screening Committee of UK lists 22 criteria that should be met before a screening program is introduced. Oral cancer screening should meet at least three of these criteria. It is unlikely, though, that oral cancer screening programs will be implemented without more scientific support of their efficacy. , Conventional visual cancer screenings for some anatomic locations can be highly successful. But the simple visual examination, however, is well known to be limited by subjective interpretation and by the potential, albeit rare, occurrence of dysplasia and early oral squamous cell carcinoma (OSCC) within areas of normal-looking oral mucosa. As a consequence, adjunctive techniques have been suggested to increase our ability to differentiate between benign abnormalities and dysplastic/malignant changes as well as identify areas of dysplasia/early OSCC that are not visible to naked eye. Screening aids of oral cancer and precancer are classified as follows. 
Classification of screening aids to oral cancer and precancer
1. Standard screening test
2. Established screening adjuncts
- Oral cytology
- Oral brush biopsy
3. Vital staining
- Toluidine blue (TB) (tolonium chloride)
- Lugol's Iodine
- Methylene Blue
4. Light-based detection systems
- ViziLite plus
- MicroLux DL
Standard screening test
Conventional oral examination
An oral visual examination carefully performed by doctors and/or trained health workers under adequate light can lead to early detection of cancer and its precursors.  5-15% of the general population has oral mucosal abnormalities, which are clinically/biologically benign. COE cannot discriminate between lesions that are progressive or become malignant and those non-progressive counterparts. COE may miss the detection of precancerous lesions that appear clinically normal.
Thus, while COE is a useful tool in detecting some oral cancer lesions, it does not identify all potentially premalignant lesions. The sensitivity and specificity varied between 58-94% and 76-98% respectively in various studies. ,,
Established screening adjuncts
Cytology has been widely accepted as a tool in the early diagnosis of cancer which has gained popularity within a short period of time since its introduction by George Papanicolaou in 1942.  Cytologic recognition of premalignant lesion in various areas of the human body is still in its infancy. Cytology is cheaper and easy procedure that can be carried out at outdoor patient department to diagnose malignancy at early stage.
Oral cytology is carried out to detect cancer pre-invasive stage by use of exfoliative cytology and to explore the possibility of using this technique in diagnosis of other oral lesions considered as premalignant ones. The cytological examination had failed to diagnose cases of malignancy accurately as that of the histopathology. The concept of cytological studies was to study the cells, which are exfoliating due to pathologic or physiologic process. In earlier days cotton swabs were used for collection of smears and this was followed by wooden or metal spatulas. This technique collects only cells of the superficial layers. So methods of collection of cells were modified. In cytology, the sensitivity and specificity differs due to the variation in subjective interpretation or due to the poor technique in obtaining cells and smear preparation.
The basis for development of newer techniques for collection of cells is, dysplasia starts in basal layers (stratum germinatum) and extends to all the layers of the epithelium. The oral CDx cytobrush claims to collect the basal layer cells non-invasively and assess the dysplasia by computer-assisted neural network, inorder to eliminate subjective misinterpretations. However, many studies showed that the cytobrush has its limitations , in sensitivity and specificity. The oral CDx system can be complemented to achive maximum accuracy by using deoxyribo nucleic acid (DNA) cytometry, silver nucleolar organisation regions (AgNOR) analysis, immunocytochemistry and fluorescent insitu hybridization (FISH). ,
Toluidine blue (tolonium chloride)
TB, also known as tolonium chloride (synthesized by Abbott laboratories in 1949 Journal of American Medical Association, JAMA), is a vital dye that is believed to stain nucleic acids. Analysis of current evidence suggests that TB is good at detecting carcinomas, but its sensitivity in detecting dysplasias is significantly lower. ,, Furthermore, there remain a high percentage of false-positive stains, which impairs its use in primary care settings as a valid screening mean. In addition, controversy exists regarding the subjective interpretation of mucosal staining and criteria for positive results (e.g., dark royal blue versus pale blue staining).
At present, TB is best used by experienced clinicians as an adjunct to clinical examination in the evaluation of the biologic potential of potentially malignant oral lesions. A recent study by Moyer, showed that TB preferentially stained visible lesions with high risk molecular patterns and predicted risk and outcome in cases where little to no microscopic evidence of dysplasia was present.  Siar in 2005 evaluated the chemiluminescence in detecting oral cancer and potentially malignant lesions by comparing it against 1% Tolonium chloride mouth rinse.  Accuracy was reported as 80.6% for chemiluminescence, whereas, 64.5% was the accuracy report for Tolonium chloride mouth rinses. In a study by Zhang, et al. TB might be useful in determining clinically evident oral lesion, which are more likely to progress to oral cancer.  To date, however, research has not been extended to determine whether TB can identify and predict the risk of progression for epithelial abnormalities that cannot be seen with the naked eye.
Interpretation of the TB stain
- Dark blue stain was considered as positive for lesions suspicious malignancy
- Light blue retention was considered as positive for premalignant lesions unless proved otherwise by biopsy
- The lesions without any retention of stain were considered as negative.
- Indicates area for biopsy
- Low cost
- Non-invasive (no local anesthetic, suture, virtually pain free)
- Disposable device (no cross-contamination)
- 100% sensitivity for pathology
- Patient is aware he or she received an oral cancer examination.
- TB stain can remain in mouth for 4-6 h
- Specificity: Not meant to be a diagnostic tool; it is a screening device only
- False positive reactions were noticed in case of respiratory epithelium
- Abrasions, ulcers, granulation tissue take up the stain falsely.
TB has been used to diagnose inflammatory, malignant cells, Bronchogenic carcinoma, extent of malignant epithelial lesion, chemically induced dysplasias and carcinoma of the hamster cheek pouch and to identify precancerous lesions and to choose sites for biopsy.
Lugol (1829) a French physician was the first person to develop Lugol's iodine (also called Lugol's solution) consisting of 10 parts of potassium iodide to 5 parts of iodine to 85 parts of (distilled) water. Lugol suggested that his iodine solution could be used to treat tuberculosis. For almost up to the end of the 19 th century it was used as an antiseptic. Schiller described Iodine test, which was used to delineate areas that were likely to contain cervical precancers. Glycogen containing squamous epithelium was fully differentiated when stained strongly with iodine, giving rise to the so-called iodine positive state. Other epithelia that failed to take up the stains were called iodine negative and included columnar epithelium, immature metaplastic squamous epithelium, orthokeratinized epithelium and some invasive cancers.
Epstein, et al. compared lugols with TB stain and said the disadvantages of the both stains can be overcomed by using both the stains to accurately diagnose the lesions.
Composition: 5 g iodin (I 2 ) + 10 g potassium iodide + Distilled water 100 ml
Application of iodine results in brown or black color staining in areas containing glycogen [Figure 1] and [Figure 2]. In areas lacking glycogen, iodine is not absorbed and such areas remain colorless or turn yellow. The stronger and more consistent the light source, the easier it will be for health care providers to identify abnormalities.
- It can be used for non-keratinized stratified squamous epithelium
- Simple, easy-to-learn approach that is minimally reliant upon infrastructure
- Low start-up and sustaining costs
- Many types of health care providers can perform the procedure
- High sensitivity results in a low proportion of false negatives
- Test results are available immediately
- Decreased loss to follow-up.
- It is an irritant that damages normal epithelium
- Patient complaints of abdominal pain, heart burn and nausea
- Allergic reaction to iodine
- Induces shock some times
- Less accurate when used in post-menopausal women.
- Used routinely in patients at risk - those with head and neck cancer
- Heavy smokers and drinkers.
It is a heterocyclic aromatic chemical compound. At room temperature appears as a solid, odorless, dark-green powder, which yields a blue solution when dissolved in water.  Recent research suggests that methylene blue, TB, and other 3,7-diaminophenothiazinium-based redox cyclers induce selective cancer cell apoptosis by NAD (P) H: Quinone oxidoreductase (NQO1) (NQO1 NAD (P) H dehydrogenase, quinone 1)-dependent bioreductive generation of cellular oxidative stress.  Combined with plant auxin (indole-3-acetic acid), methylene blue is being investigated for the photodynamic treatment of cancer.  Considering its low toxicity and the fact that it is cheaper than TB, it may be convenient to substitute it for TB in large-scale oral screening in high-risk patients. 
- Early detection of suspected oral cancer
- Methylene blue has been used to detect gastric, prostate, and bladder cancers
- It is used as a treatment for Alzheimer's disease
- Methylene blue can also be used to examine ribo nucleic acid (RNA) or DNA under the microscope as well as in northern blotting technique.
Light-based detection systems
Chemiluminiscence refers to the emission of light from a chemical reaction which is of varying degrees of intensity with colors that span the visual spectrum. The relevant technology (ViziLite system - Zila Pharmaceuticals, Phoenix, AZ), involves the use of an oral rinse with a 1% acetic acid solution for 1 min followed by the examination of the oral mucosa under diffuse chemiluminescent blue/white light (wavelength of 490-510 nm). , The theory behind this technique is that the acetic acid removes the glycoprotein barrier and slightly desiccates the oral mucosa; the abnormal cells of the mucosa then absorb and reflect the blue/white light in a different way with respect to normal cells. Hence normal mucosa appears blue, whereas abnormal mucosal areas reflect the light (due to higher nuclear/cytoplasmic ratio of epithelial cells) and appear more acetowhite with brighter, sharper and more distinct margins.
More recently, the ViziLite system was modified in order to include the use of TB and a new chemiluminescence device (MicroLux DL) was introduced.  Several studies have been performed with the Vizilite system with the attempt to demonstrate its efficacy to enhance the identification of mucosal abnormalities. The majority of studies have investigated how chemiluminescence enhances subjective clinical evaluation of intra-oral lesions, including brightness, sharpness and texture with respect to routine clinical examination.
As these parameters are highly subjective, it is not surprising that results have been contradictory. Whilst some authors report that this technique can improve the detection of intra-oral abnormalities (regardless their nature), other reported that the overall detection rate was not significantly improved and the chemiluminescent light produced reflections that made visualization even more difficult than with incandescent light.
In studies by Epstein, Huber, Kerr et al., and Oh et al. ,,, suggest that chemiluminescence may help identifying occult lesions that cannot be seen with incandescent light but this, however, is not supported by any strong evidence. ,,
Principle of action
Following the application of a cytoplasmic dehydration agent such as an acetic acid solution, leukoplakic lesions are better visualized due to changes in their refractile properties. This occurs in atypical non-keratinized squamous epithelium due to an increase in the nuclear: Cytoplasmic ratio of the cells.
- Vizilite has the advantage in that it is capable of delineating the sharp borders between normal and abnormal oral mucosa and often extended beyond the clinically identified outline
- Malignant lesions could be recognized without the aid of adjunctive diagnostic tools
- To screen for the possibility of field cancer change in other parts of the apparently normal mucosa.
- It is used to diagnose leukoplakias and radiation mucositis
- Identification of asymptomatic and clinically non-evident lesions
- Diagnostic aid for the detection of oral cancer and pre malignant early lesions (PMELs).
VELscope is intended to be used by a dentist or health-care provider as an adjunct to traditional oral examination by incandescent light to enhance the visualization of oral mucosal abnormalities that may not be apparent or visible to the naked eye, such as oral cancer or premalignant dysplasia. VELscope is further intended to be used by a surgeon to help identify diseased tissue around a clinically apparent lesion and thus aid in determining the appropriate margin for surgical excision.  The summary also states that VELscope is complementary to, and is intended to be used in combination with, a traditional oral mucosal examination with white light. The difference between VELscope system and the predicate device is that VELscope uses filters to block the reflected blue light to allow the visualization of the natural tissue fluorescence.
Patton et al. in 2008  and Anna Trullenque-Eriksson  et al. in 2009 conducted a systematic review to evaluate the effectiveness of adjunctive techniques including TB, ViziLite Plus with TB, ViziLite, VELScope, and Oral CDx brush biopsy for oral cancer examination and lesion diagnosis and concluded that, given the lack of effectiveness data in general dental practice settings, clinicians must rely on a thorough oral mucosal examination supported by specialty referral and/or tissue biopsy for oral premalignant and malignant lesion [Figure 3].
- When cells interact with light they become excited and re-emit light of varying colors (fluorescence) and this can be detected by sensitive detectors
- All tissues fluoresce due to the presence of fluorescent fluorophores with in them (autofluorescence)
- Florescence spectroscopy and imaging can detect these substances and provide characteristic spectra that reflect biochemical changes occurring within tissues.
- The VELscope examination takes only 1-2 min and is painless and non-invasive, with no stains or rinses required
- Improves the distinction between normal and abnormal tissues (both benign and malignant malignant
- Useful adjunct to a thorough visual and digital soft tissue clinical examination
- Possesses useful benefit in the determination of surgical borders and post-surgical evaluations.
- It covers large surface area
- Non invasion method
- Small lesions can be identified.
- Tongue depressors and/or mirror reported easier to use than unit's VELtractor cheek retractor and heat from prolonged and close tissue examination may cause patient discomfort.
It is used for soft-tissue examination in the diagnosis of suspicious oral and surgical borders.
- Analysis of small sample sizes
- Lack of methodologically sound clinical trials
- Insufficient use of histologic and molecular mapping of optically altered mucosa
- Factors that can affect the optical qualities of the oral mucosa (e.g., inflammation, previous chemo- or radio-therapy)
- Direct comparison with other detection methods.
| Conclusion|| |
Improving oral cancer detection and diagnosis have long been major challenging facing both dental and medical providers around the globe. Screening and early detection in population at risk have been proposed to decrease both morbidity and mortality associated with the oral cancer. However, the subjective interpretation of the innocuous lesions by COE with the vivo examination tests drastically improved the diagnosis at an early stage. Many diagnostic methods are tried to eliminate surgical biopsy which is the golden standard, but these tests are not the alternative for surgical biopsy rather, they can be adjuvant. All the newer methods should be analyzed with methodologically sound clinical-trails, which should be compared, qualified and quantified with that of surgical biopsy.
The major goals of advanced diagnostics are to move ex vivo tests to in vivo diagnostics by visualizing functional parameters of tumors and tumor cells. Understanding of cells functional physiology in growth survival and interaction with the matrix constituents of their milieu and ability to monitor lesions in vivo hold great promise for study of potentially malignant lesions and preventive intervention. Application of these highly advanced technologies in diagnosis of tumors improves the patient care.
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[Figure 1], [Figure 2], [Figure 3]