Most diagnoses can be established by a combination of a thorough medical history and examination with evidence from a variety of tests (blood, urine, microbiology) and imaging information (X-ray, MRI, CT, ultrasound) as required. In some cases additional examination of samples of tissue or cells, a biopsy, is necessary either to confirm or to exclude certain conditions. A biopsy is not usually the first line of investigation because of its invasive nature.
In a maxillofacial clinic the most common reasons for a biopsy are to exclude serious pathology (often in patches of white mucosa or other growths of mucosa) or to obtain further and/or definitive diagnostic information about suspected cysts, salivary gland problems and all kinds of lumps, benign and malignant. The purpose of a biopsy is to confirm absence or presence of certain conditions, in addition to examining the extent of certain conditions.
There are various kinds of biopsies, almost all of them can be undertaken in a clinic or outpatient setting. Biopsies can be taken of hard (bone) and soft tissues, or can be used to extract cells and/or fluids. In most cases biopsies are carried out under local anaesthesia.
An excisional biopsy is the most comprehensive variety: the entire lesion is removed and the removed tissue is investigated afterwards. Logic suggests that an excisional biopsy is the method of choice if the lesion needs removing and can be removed in a straightforward way, irrespective of its exact nature. This combined diagnostic and therapeutic approach saves a second surgical intervention later on.
An incisional biopsy or a core needle biopsy remove only some of the tissue of a lesion but do not aim to remove the entire lesion in the session. It is obviously important to choose a representative area of the lesion for taking specimen tissue; it is mainly for this reason that often more than one small sample is taken.
An incisional biopsy for lesions on or near the body surface uses a small incision to extract a tissue sample, or several samples. A scalpel or some special cutting device (which functions similarly to a cookie cutter, called a punch biopsy) may be used to obtain the sample.
A core needle biopsy uses a range of needles to extract an intact rod of lesion tissue (similar to extracting columns of arctic ice, core samples, by drilling with – very large – core needles into the arctic ice sheet in climate research). Needle biopsies may require guiding by imaging methods usually to ensure optimal placement of the needle in the lesion. A common such imaging guide for needle biopsies in the head and neck region is ultrasound scanning but other imaging techniques (MRI or CT (X-ray)) in principle are also available for the purpose.
Fine needle aspiration biopsies (also called fine needle aspiration cytology, FNAC) differ in that these biopsies do not extract a preserved small specimen of tissue but only draw cells or fluids by means of a thin needle connected to a syringe.
In addition, histopathological examinations also have a role during and after surgery. All surgically removed specimens are sent to the pathology laboratory for final assessment. When malignant lesions are surgically removed, a quick ‘on the fly’ examination (under a microscope) of frozen sections of the resected tissue from the margin of the specimen can help to determine if the surgical margin is clear (‘negative margin’, that is healthy issue) or if a wider excision is necessary if a ‘positive margin’ is found. This is popular in some countries and can be useful in circumstances where it is important to keep the excision margin safe but at a minimum. Mohs’ surgery in the treatment of facial skin cancer is a very specialised variation of the principle where chemically prepared sections are examined.
A thorough pathological and histological examination of a tissue sample from a biopsy usually takes several days and involves a range of investigations. The aim of these investigations is to unambiguously classify the lesion tissue. In the vast majority of cases this classification (diagnosis) is achieved but some conditions do present a challenge for definitive clinical and histological / pathological diagnosis (for example, polymorphous low grade adenocarcinoma of salivary glands may need several expert reviews).
Pathology and histology (microscopic structure of tissues) examination includes assessment of the tissue under a microscope and requires preparations of small parts of the sample for microscopic (histology) and further biochemical investigations. The pathology laboratory reports back to the surgeon who will share and explain the results in a follow-up meeting.
Next section: Biopsy