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Securing the diagnosis is fundamental to safe and successful management of the patient and will depend on a clear and concise history, careful clinical examination and the use of additional special investigations including radiography, biopsy and other laboratory and diagnostic techniques. Within this spectrum, biopsy is a commonly performed test. Should the lesion appear malignant, biopsy should not be performed in general practice, but the patient should be referred immediately for a specialist opinion.
Indication for biopsy:
Where the diagnosis is clinically evident as in the case of fibroepithelial polyps, viral papillomas or mucous cysts, biopsy is not required for diagnosis although where treatment involves excision, the specimen should always be submitted for histological confirmation. If there is doubt or the lesion is arising deep to the mucosa then histological diagnosis is essential.
Biopsy:
Biopsy is defined as the complete or partial removal of a lesion for laboratory examination to aid definitive diagnosis.
Whereas biopsy usually establishes the definitive diagnosis, there are occasions when the result is not clear and in these circumstances the available histological data must be measured against clinical findings.
Biopsy techniques:
Excisional biopsy
This is the ideal approach for small superficial lesions less than 1 cm in diameter, where the clinical appearance suggests that it is benign. Most if not all of these procedures can be performed using local anaesthesia (LA). Where regional blocks are not performed, the local anaesthetic should be injected at a distance from the lesion to avoid distortion of the tissue at the operating site.
Superficial lesions such as fibroepithelial polyps and squamous papillomas that are pedunculated (arising from a narrow stalk) can be excised by simple division of the base of the pedicle where it arises from the mucosa. For papillomas that have a viral aetiology some surgeons like to use electrosurgery.
For larger and sessile lesions (broad-based) excision should be based on an elliptical incision. This is made around the base of the lesion (No. 15 blade) and should include a 1- to 2-mm margin of normal tissue. Choice of such an incision is aimed at creating a wound that will appose without redundant tissue (dog ears) and close without tension, because the ellipse needs to be at least twice as long as it is broad. A suture may be placed at the edge of the ellipse to hold the tissue. This will avoid crushing the specimen with tissue forceps. It can be used to retract the specimen during dissection with scissors or scalpel. When dissecting the specimen free it is important to avoid damaging underlying structures such as blood vessels and nerves by using ‘blunt dissection’ (described below).
To excise submucosal lesions the covering mucosa needs to be divided to develop access and establish the plane of dissection. This is therefore more complicated than excision of superficial lesions. The orientation of the incision will be along the longest dimension of the lesion but must also take into account anatomical relationships such as the opening of the parotid duct or the mental nerve. For large or superficial lesions such as mucous cysts that have thinned the mucosa this technique can be modified to an elliptical incision to include a portion of the covering mucosa. This will reduce the risk of rupture, or perforation of the lesion at the superficial aspect, but will mean sacrificing the overlying mucosa.
To avoid distortion the outline of the incision can be marked using a surgical pen before the introduction of LA. The initial incision should divide the mucosa but not penetrate the specimen, so the depth will vary depending on the site and depth of the lesion. Superficial lesions covered by thin mucosa, as found in the fl oor of the mouth or lower lip, will require very careful work to avoid related anatomical structures. Following the incision, a combination of sharp and blunt dissection is required to define the plane of dissection and then deliver the lesion. In the main, blunt dissection is advised as it will define the tissue plane around the lesion and avoid damage to adjacent structures such as blood vessels and nerves.
In this technique blunt-ended scissors are introduced into the tissues at the margin of the lesion with the points together. The points are then separated, forcing the tissues apart along their natural planes and the instrument is withdrawn with the blades open so there is no cutting action. The process is best started away from the ‘thin’ covering mucosa or superficial part of the lesion as it is easier to get the plane identified and started. Dissection is then repeated from various angles to ‘develop’ the plane all around the lesion. As required, sharp dissection either with a scalpel or by cutting with scissors may also be used to finally deliver the specimen. During this stage of the process great care must be taken to prevent damage to adjacent and underlying structures, and to avoid perforating the lesion.
Incisional biopsy:
This technique is indicated in cases where the diagnosis is in doubt (i.e. possible malignancy or potential for recurrence) and complete excision, in one stage under LA, is impractical in terms of size, complexity and/or the patient’s ability to cope with the surgery.
In the hospital context, if there is a suspicion of malignancy, the biopsy must be taken from a representative part of the lesion and include a suitable edge of normal tissue. This allows the sample to be held at the normal tissue margin and thereby avoids introducing surgical artifact. It also gives some idea of the pattern of invasion at the interface. An elliptical incision is suitable, with a sharp dissection technique using a scalpel and scissors. If the biopsy is of a mucosal lesion such as leukoplakia, it is important to take a deep enough specimen to get into connective tissue (approx. 6 mm) and to take a broad enough piece, so that after processing there will still be sufficient for a number of complete sections to be cut from it in the laboratory (at least 4 mm). Where the field of mucosal abnormality is extensive, it may be necessary to carry out multiple incisional biopsies. If this technique is carried out, it is important to draw a diagram of the lesion to make orientation clear for the pathologist.
For large, solid submucosal swellings, particularly in the palate where the risk of minor salivary gland malignancy is high, incisional biopsy is often the procedure of choice but this decision carries significant implications for further management and therefore should be left to specialists.
Other biopsy techniques:
Punch biopsy
A circular blade can be used to remove a cylindrical core of tissue as a form of incisional biopsy: this punch biopsy technique is more commonly used on skin.
Trephines
In this technique a core of tissue is trephined from the lesion. It may be used for soft-tissue swellings or bone. This provides sufficient material, retaining tissue architecture, for histological diagnosis and is useful for lesions where access may be difficult.
Cytology
This technique is based on microscopic sampling of tissue either by fine needle aspiration (FNA) or by using an abrasive technique such as brush or swab (exfoliative cytology). Both aim to remove cells representative of the lesion, which are then transferred to microscope slides and prepared for histo-cytological assay. These are investigations that require special equipment and skill in both taking the sample and preparing the slides and, as such, are best referred to operators with the appropriate experience. All such methods lack the advantage of maintaining tissue architecture, but offer a relatively quick and minimally invasive approach to biopsy.
Aspiration biopsy
Fine-needle aspiration cytology is a useful method for sampling soft-tissue masses in the head and neck, such as lymph nodes and salivary glands. A 10- or 20-mL syringe with a 21-gauge needle is installed into a specially designed holder which facilitates the safe and controlled introduction of the needle, and allows aspiration at variable pressures. The needle is inserted into the centre of the deep tissue mass and the plunger pulled back, drawing a small ‘core’ tissue sample into the needle. The needle tip is resited within the lesion and the procedure repeated several times. The sample is then delivered directly onto a microscope slide, spread and fixed. This is a valuable method but technique sensitive. Accurate sampling is clearly essential and on occasions where the lesion is deep it can be combined with ultrasound investigation to ensure the needle is positioned within the lesion (ultrasound-guided FNA).
Smears
Cytological smears can be used to sample the surface of epithelial lesions, especially where the lesion is not heavily keratinized, in which case it is possible to harvest cells deeper within the epithelium. The technique could be used as an adjunct to biopsy for monitoring widespread lesions, which may undergo malignant transformation. A diagnosis of malignancy based on cytology alone would be considered insufficient by most pathologists and formal histological sampling would be required before proceeding to cancer treatment.
Completing a pathology request form
- Patient details: name, gender, race, age, address, medical and social history
- Clinical details
- History: symptoms, previous biopsy and treatment
- Examination: signs, size, shape, position, texture,
- colour
- Investigations: microbiology, haematology, radiology
- Biopsy type
- Previous biopsy number/s
- Orientation: use a diagram
- Clinical diagnosis
Also ensure that the specimen pot is clearly marked with the patient’s name and other identification information (such as hospital number or date of birth).
Overview:
Methods of biopsy
- Excisional: complete removal with surrounding normal tissue (width and depth)—for small and presumed benign lesions
- Incisional: removal of a portion of normal and abnormal tissue—for larger lesions to establish the diagnosis and subsequent treatment options including potentially malignant lesions
- Punch: core of abnormal tissue—rarely performed in the mouth
- Trephine: Removes core of tissue suitable for deepseated lesions
- Aspiration: fine-needle aspiration cytology, for deep soft-tissue lesions, such as potentially malignant neck lymph nodes; technique sensitive
- Cytology: abrasive removal of superficial cells (±) deeper cells
Further reading
- Barnes L. (ed.) (2005) Pathology and genetics of head and neck tumours. IARC Press, Lyon, France.
- Cawson R. A., Binnie W. H., Barrett A. W., Wright J. M. (2001) Oral disease clinical and pathological correlations, 3rd edn. Mosby, St Louis, MO, Chs. 6, 7, 8 & 10.
- Kramer I. R. H., Pindborg J. J., Shear M. (1992) Histological typing of odontogenic tumours. Springer Verlag, Heidelberg, Germany.
- Peterson L. J., Ellis E., Hupp J. R., Tucker M. R. (eds.) (1997) Contemporary oral and maxillofacial surgery, 3rd edn. Mosby, St Louis, MO, Ch. 23, pp. 512–532.
- Waites E. (2002) Essentials of dental radiography and radiology, 3rd edn. Harcourt Health Sciences, Edinburgh.
