Investigation
Surgical biopsy
A clinical diagnosis of oral cancer should
always be confirmed histologically. Within the oral cavity a surgical biopsy can
nearly always be obtained using local anaesthesia. An incisional biopsy is
recommended in all cases. Whenever possible the patient should be seen at a
combined clinic by a surgeon and radiotherapist before even the biopsy is
carried out, but provided careful records are made an initial incisional biopsy
is acceptable and may save time in the planning and execution of subsequent
therapy. The biopsy should include the most suspicious area of the lesion and
include some normal adjacent mucosa. Areas of necrosis or gross infection should
be avoided as they may confuse the diagnosis.
Fine needle
aspiration biopsy
This technique is applicable mainly to lumps
in the neck, especially suspicious lymph nodes in a patient with a known primary
carcinoma. It consists of the percutaneous puncture of the mass with a fine
needle and aspiration of material for cytological examination. The method of
aspiration needs no specialised equipment and is fast, almost painless and without
complications. The node is fixed between finger and thumb and then punctured by
a 21G or 23G needle on a 10-ml syringe, the gauge of the needle depending on the
size of the node. Important points to note are that the needle is properly
pushed on to the syringe to prevent air leaking in when the plunger is withdrawn
and that a small amount of air is already in the syringe (about 2 ml) before the
node is punctured in order subsequently to expel the aspirate from the needle on
to the slide.
Radiography
Plain radiography is of limited value in the
investigation of oral cancer. At least 50 per cent of the calcified component of
bone must be lost before any radiographic change is apparent. Furthermore, the
facial bones are of such a complexity that confusion from overlying structures
makes X-ray diagnosis more difficult. However, rotational pantomography of the
jaws can be helpful in assessing alveolar and antral involvement, provided that
the above limitations are understood.
Computerised
tomography
The increasing availability of computerised
tomography (CT) scanning has undoubtedly been of great benefit in the investigation
of head and neck tumours. However, for intraoral tumours its value is more
limited. For the evaluation of antral tumours, particularly assessment of the
pterygoid regions, CT has superseded plain radiography and conventional
tomography. CT is also of value in the investigation of metastatic disease in
the lungs, liver and skeleton.
Radionuclide
studies
Technetium (Tc) pertechnetate bone scans of
the facial skeleton are of little value in the diagnosis of primary oral
cancers. There will be obvious clinical disease long before bone changes are
visible on a Tc scan. Furthermore, such scans are nor specific and will show
increased uptake wherever there is increased metabolic activity in the bone.
Ultrasound
Abdominal ultrasound to detect liver
metastases is probably as accurate as CT scanning. As it is noninvasive, readily
available and cost effective, it is probably the most appropriate technique
for assessing the liver.