Updated: August 2006
4.1 Clinico-pathologic Considerations
Malignancy should be suspected in the following situations and further investigation undertaken:
- An area of ulceration or induration in the oral cavity without obvious cause and not quickly responding to symptomatic treatment
- Pain in the mouth, jaw or ear without obvious cause
- Unexplained malfunction of swallowing or speech
- Areas of ulceration produced, in theory, by ill-fitting dentures or jagged teeth that do not resolve quickly when potential irritants are removed
- Tonsillitis, especially unilateral, that does not resolve rapidly with treatment
- Unexplained, enlarged lymph nodes in the neck
- Solitary masses in the thyroid or changes in pre-existing goiters
- Palpable lesions in salivary glands, especially when they are asymptomatic.
4.2 Diagnostic and Treatment Planning Considerations
Biopsy of the primary lesion is the first procedure and, following diagnosis, treatment planning can be decided in consultation. Molecular markers are becoming increasingly more important in the development of management plans for individual patients. The tests used to identify these markers require adequate tissue samples so it is important that as much tissue as is reasonably attainable is taken at the initial biopsy.
The subsequent management of a patient may be compromised if tissue planes in the neck are disrupted by a diagnostic open biopsy, so this should only be done when all other methods of diagnosis have failed.
There are pathologists throughout the province who can give a high rate of accurate diagnosis of lymph node abnormalities on fine needle aspiration. This is especially so for metastatic squamous carcinoma. A high degree of accuracy is also possible in salivary gland tumours and thyroid nodules. If, however, a lesion is clinically suspicious of malignancy and fine needle aspiration does not confirm this, repeat aspiration or other means of biopsy must be undertaken. There is also the possibility of a false positive diagnosis and, if fine needle aspiration indicates a diagnosis of malignancy in a clinically benign situation, the biopsy should be repeated before planning treatment.
Detailed imaging of the primary tumour and regional lymph node drainages areas is usually invaluable in the pretreatment assessment of all but the earliest tumours. The relative indications for currently available imaging modalities are as follows.
Adequate initial diagnosis is essential to determine whether surgical intervention or only conservative management is required. Following history and physical examination, the following diagnostic pathway is proposed.
The differentiation between a cystic and solid thyroid nodule can be made by a fine needle aspiration biopsy (FNA) or by ultrasonography. The advantage of an early FNA is that material can be obtained from all lesions for cytological analysis and should be preferred in all cases. If malignant cells are detected or interpreted as follicular neoplasia, surgical intervention should be recommended without unnecessary delay. If the cytology is suspicious or non-diagnostic, a repeat FNA may be done. If diagnosis is still unclear then radioactive isotope uptake and scanning should be done to determine whether the nodule is either hot or cold. If the nodule is hot, (a solitary autonomous nodule), then the patient could be merely observed and have medical treatment as required. On the other hand, if the nodule is not hot (cold), surgical intervention should be recommended. Repeat fine needle aspiration biopsy may be recommended if the thyroid nodule fails to regress. If again this proved to be suspicious then surgery should be recommended.
These have limited value in most cases, but are useful for demonstrating gross bony involvement or soft tissue swelling, for following sinusitis (esp. maxillary sinusitis) and evaluating the gross position of brachytherapy implants.
CT is presently the primary modality for the assessment of primary ENT tumours and nodal metastases. CT has inherently higher patient throughput compared to MRI and equal (or better) spatial resolution. It is the best modality for assessing the extent of lytic skull base involvement. A disadvantage is the marked artifact from dental amalgam and implanted orthopedic metal which may render parts of the study almost uninterpretable. These problems can be minimized by using different imaging planes. In addition, CT ENT assessment is moderately dependent on the use of iodinated contrast and contrast allergy may be a problem.
The Radiologist will decide on the exact protocol based on the information provided by the clinician and data from previous studies. It is therefore essential that appropriate information is provided for the radiologist. However, in most cases of head and neck cancer assessment of the primary tumour and regional nodes requires scans with IV iodinated contrast with axial 3mm cuts taken from the base of skull to the clavicles.
If enhanced visualization of structures whose long axis is parallel to the transverse plane is required, then 3mm coronal cuts are also helpful. This would include tumours involving the skull base, cavernous sinus, floor of the sphenoid sinus or nasopharyngeal roof, or the palate. Coronal views are also helpful for assessing the 3-dimensional relationships of complex tumours involving multiple structures. They can not be used for patients who are unable to extend their neck due to arthritis or instability.
Compared to CT, MRI relies on completely different physical mechanisms to obtain an image – the MR signal is obtained from mobile protons in water and fat whereas CT images are based on electron density. Soft tissue contrast is generally better in MRI, particularly close to bone where there is often some degradation of the soft tissue imaging with CT – in general subtle lesions are easier to see. Hence MRI is better for seeing structures around the pituitary fossa, or soft tissue lesions invading the cavernous sinus, the skull base and its foramina, sphenoid floor and nasopharyngeal roof, the palate and within the spinal canal. MRI is indicated for lesions with complex 3-D topology, such as some tongue cancers, where demonstration of bony margins is not of prime importance. This holds true even when no MRI contrast (gadolinium) is used. Occasionally malignant tissue is more easily differentiated from an inflammatory process (eg: in differentiating between tumour and benign inflammatory mucosal disease in cranial air sinuses).
Imaging can be performed in any plane the operator desires (CT is restricted to transverse and coronal planes). Vessels can be imaged non-invasively using "MR-angiography" protocols. MRI contrast agent (gadolinium) has several advantages. The incidence of contrast allergy is extremely low. Gadolinium is excreted primarily in the liver hence it can be used in patients with impaired renal function.
Disadvantages: MRI does not image bone directly and is poor for following lytic bony lesions. Some people cannot be placed in the MRI magnet bore (eg. they are claustrophobic, or have a pacemaker, etc.). They must be able to lie perfectly still for 4-8 minutes at a time; otherwise the image quality is degraded. CT requires the patient to lie still for approx. 30 seconds. Occasionally embedded ferromagnetic foreign bodies can produce marked artifact which makes image interpretation difficult or impossible.
The use of positron emission tomography (PET) is becoming more widespread worldwide in the management of patients with cancer. Numerous studies have demonstrated that squamous cell carcinomas of the head and neck region are well imaged by PET and there is accumulating evidence supporting its use for a number of indications in head and neck cancers.
Effective August 16, 2005, the Functional Imaging Department has expanded the clinical indications for referral within the framework of the evidence-based BCCA guidelines for FDG-PET. PET/CT scan referrals will now be accepted at our facility for certain indications in adult oncology patients. To view the referral guideline, please go to the Functional Imaging page.
There is support in the literature for the use of PET in three main areas:
- In the initial staging of head and neck tumours where there is some uncertainty as to how extensive initial surgery or radiotherapy should be.
- As an additional procedure in the diagnosis of carcinoma of unknown primary presenting as a nodal neck mass.
- In the detection of recurrent disease post therapy where standard investigations are equivocal and further salvage therapy is feasible.
