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points to note are that the needle is properly pushed on to the syringe to prevent air leaking in when the plunger is withdrawn and that a small amount of air is already in the syringe (about 2 ml) before the node is punctured in order subsequently to expel the aspirate from the needle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 For the evaluation of antral tumours, particularly assessment of the pterygoid regions, CT has superseded plain radiography and conventional tomography.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.