Cancers of the oral cavity are diagnosed after the patient presents with the symptoms of the condition. This is more often than not a long persistent lesion, swelling or ulcer within the mouth.
Early oral cancers can also be detected during a routine dental check up. Once suspected the patient is immediately referred to an ear, nose and throat specialist or a specialist in head and neck cancers.
The process of diagnosis of mouth cancer includes a medical examination, biopsy and so forth. 1-5
A thorough and complete examination of the mouth, throat and neck is performed. This is done by visualization by the naked eyes as well as by a fine flexible tube with a camera on its tip. This is called a nasendoscope.
An endoscope has a dual purpose – it can examine the insides of the mouth for abnormal tissues and take samples of tissues for microscopic examination.
Visualization may also be done using special instruments. Light-based Detection Systems use chemiluminescence, blue white LED and sometimes auto fluorescence as light sources to detect cancers in the mouth. They are designed to detect abnormalities that are not necessarily visible to the naked eye.
These systems commonly used 1% acetic acid rinse of the mouth to remove external debris and to make cell nuclei in the inner linings of the mouth more prominent.
The patient rinses with the acid for 30-60 seconds. The health care provider then examines the oral cavity with the light source.
Abnormal epithelium will appear exceedingly white. Normal cells appear light blue in color in contrast. The test itself takes approximately five minutes.
Biopsy and fine needle aspiration cytology (FNAC)
Biopsy and fine needle aspiration cytology (FNAC) is performed if cancer is suspected. The area affected is first numbed with a local anesthetic and a thin needle is passed into it to withdraw small amount of tissues. This is called FNAC.
In some cases a small surgery is performed and a larger amount of tissue is excised. This is called a tissue or punch biopsy. The tissues are then fixed with special dyes and stains onto a slide and examined under the microscope for cancer.
FNAC and biopsy may also be performed on swollen lymph nodes and this may provide clues about spread of the cancer as well. A panendoscopy and removal of tissues on endoscopy of the oral cavity and the lesions may also be performed.
Brush Cytology is another form of oral biopsy. It is also called transepithelial oral brush biopsy. It can detect lesions that have the potential to turn into cancers.
A sample of the lesion is collected with a small brush that is rotated 5-15 times over the lesion with firm pressure. The collected tissue is then placed on a slide and examined under the microscope using special dyes.
If the results come positive or any abnormality is seen a punch biopsy is prescribed.
Staging of mouth cancer
Once biopsy is performed the cancer is detected under the microscope. Thereafter the cancer is staged.
Staging of the cancer helps in determining the possible outcome of the cancer and also helps in planning therapy for the cancer. For example, if the cancer has spread to distant organs like liver and lungs, the outcome of the cancer is poor and chances of survival are low.
Early oral cancer is usually curable while intermediate stages are possibly curable.
Staging is performed using three basic parameters – T, N and M.
T stands for the extent and size of the tumor, N stands for possible involvement of lymph nodes and M stands for possible metastasis or spread of the cancer.
Dental x-rays are suggested to check the entire mouth. This can show whether cancer has spread to the jaw.
Other radioimaging studies
Other radioimaging studies like an MRI scan and a CT scan of the head and neck is performed to check for the exact site, extent of spread and the extent pressure on vital organs of the tumor or mass.
A CT scan or MRI of the chest and abdomen is also prescribed to check for spread of the cancer to the liver and lungs.
Positron emission tomography scan (PET scan)
A positron emission tomography scan or PET scan is also prescribed to detect the possible spread of the cancer.
The scan involves injecting the body with a special dye that contains radioactive glucose. Once inside the body the cancer cells take up the glucose selectively and this is detected as radioactive clusters on imaging with the scanner.
Grading mouth cancer
In addition to staging, the cancer is also graded.
There are three grades:
low grade (where the cancer spreads slowly)
moderate-grade (the cancer spreads at a medium pace)
high-grade (the cancer is aggressive and likely to spread quickly if not controlled)