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Abstract
The diagnosis and evaluation of laryngeal carcinoma are made by an indirect mirror examination, endoscopy and imaging studies. Endoscopy includes rigid laryngeal endoscopes (Hopkins telescope) with angled lenses (70 and 90), flexible fiberoptic endoscopes and microlaryngoscopy. Imaging studies like CT and MRI are not specific enough to evaluate early-stage of tumoural invasion immediately beneath the mucosa or inside the cartilages.
One difficulty in diagnosing laryngeal dysplasia is discriminating between normal and dysplastic tissues. At the time of operative assessment, it may be difficult for the clinician to determine the full extent of a lesion. The most common method of assessing laryngeal lesions is microlaryngoscopy, which shows gross differences in the appearance of the lesion and its surrounding mucosa. However, new methods have emerged that ultimately may assist in the assessment of premalignant and malignant laryngeal lesions.
These new examination techniques include endoscopical imaging (Autofluorescence endoscopy, contact endoscopy and endoscopic high frequency ultrasound), radiological (PET, SPECT and virtual endoscopy) and other techniques like videokymoStroboscopy, laser scanning cytometry and biological marker as P53.
Autofluorescent endoscopy is a method, which depends on the native fluorescence of the mucosa. The sensitivity of autofluorescent imaging is substantially superior to that of white light endoscopy for evaluating cancerous lesions. Increased false-positive rate for autofluorescent imaging of benign lesions, causing the specificity of the technique to be very low.
Contact endoscopy allowing mapping of the disease in different sites and in different stages. Accuracy of contact endoscopy will certainly be enhanced with improvements in the optical system, new cell dyes and markers, distinct lighting, and better imaging techniques.
Using endolaryngeal ultrasonography with a pediatric transesophageal probe during microlaryngoscopies, the anatomy of the compartments of the larynx can be systematically assessed ) preepiglottic space and paraglottic spaces).
PET may be superior to CT or MRI for detecting recurrent or residual disease when surgery or radiation has altered the usual anatomic relations. Assessment of primary tumours of the larynx with PET alone is not likely to be helpful, but newer technology combining PET and CT or MRI gives both functional and anatomic information about a tumour’s size and location.
SPECT is an alternative metabolic technique if PET was unavailable. Evaluation of laryngeal, oral cavity, oropharyngeal, and pyriform sinus tumours by SPECT is less accurate due to normal uptake in salivary and thyroid glands.
Virtual endoscopy (or computed endoscopy) is a new method of diagnosis using computer processing of 3-D image datasets (such as CT or MRI scans) to provide simulated visualizations. It shows high sensitivity in the identification of exophytic lesions of the larynx and can establish relationships between cancer and nearby structures.
Videokymostroboscopy adds another dimension to the evaluation of early glottic cancers. This technology focuses on the movement of the epithelial layer of the vocal fold relative to the underlying stroma,
p53 oncoprotein expression may be an important determinant of tumour response to radiotherapy. Since p53 gene regulates genomic stability and prevents cell cycle entry in response to DNA damage, loss of p53 function may interfere with the growth inhibiting capacity.
Laser scanning cytometer (LSC) makes possible the analysis of very small diagnostic samples, such as those obtained via fine needle aspiration biopsy.