obtained. The small risk of bleeding and infection should be explained. All equipment should be prepared and readily available before the procedure starts.
Types of biopsy
Punch biopsy
The disposable biopsy punch is usually satisfactory for diagnostic, histological samples, and is particularly useful for lesions on the inner aspects of the vulva. They are suitable for the diagnosis of most dermatoses provided the correct surgical technique is used. They range in size from 2 to 8 mm, but the minimum size should be 4 mm for an adequate specimen. The depth of the biopsy must also be sufficient, and this will need to be deeper in hyperkeratotic lesions.
Figure 7.1 Best site for biopsy in lichen planus.
Incisional biopsy
An incisional biopsy can be done from the edge of a large lesion to get a diagnostic sample.
However, care must be taken in interpretation [1], particularly for suspected malignant lesions, in which an excision biopsy should be done.
Elliptical biopsy
An ellipse of skin can be removed if it is important to compare the histological features of the lesion and peri‐lesional skin. It is also helpful when direct immunofluorescence (DIF) is needed. An ellipse can be taken across the edge of a blister or erosion and then cut in half so that the lesional half is sent for histological examination and the non‐lesional half for DIF.
Excisional biopsy
An excisional biopsy should be performed when it is important to examine the whole lesion, as in pigmented lesions, or to assess accurately for depth, as in suspected tumours.
Shave biopsy
Shave biopsies are not adequate for diagnosis, particularly for inflammatory dermatoses. They can be used to remove pedunculated lesions for histological analysis.
Local anaesthesia
Although the use of a prilocaine/lidocaine cream (EMLA®) alone has been reported to allow pain‐free punch biopsy of the vulva [2], further infiltration with lidocaine 1% or 2% is generally used. One recent study does report lower pain scores and a better overall patient experience with topical anaesthesia alone [3]. All were in non‐hair‐bearing sites, and only 5 of 37 were done with a punch biopsy; the rest were done with cervical forceps, which is never helpful for the diagnosis of vulval dermatoses as they do not provide an adequate specimen.
EMLA® applied for about 10 minutes certainly reduces the discomfort of the injected local anaesthesia, but if used, it is vital that the pathologist knows about this as it must be taken into account when interpreting the histology. Some histological features such as pale, swollen keratinocytes, basal cell vacuolation, and basal layer destruction with subepidermal cleavage are related to the use of this preparation and may lead to misdiagnosis [4, 5]. Ultrastructural changes may also be attributable to EMLA and were mistaken for lysosomal storage disease in one series [6].
The local anaesthetic is drawn up with a 21‐gauge needle and then infiltrated with a finer 30‐gauge needle just under the area to be biopsied to produce a weal. The plunger can be withdrawn to check it is not in a vessel, and in general, 1–2 ml of the local anaesthetic is adequate. It is sensible to check that the area is numb before proceeding.
Apart from the use of a topical anaesthetic prior to injection, other methods of reducing the discomfort with injected local anaesthetic include warming it to body temperature and buffering with 8.4% sodium bicarbonate.
Technique
A sterile technique is used for all types of biopsy.
1 The area is first disinfected with chlorhexidine as this allows a clear view of the lesion, which can be obstructed with other antiseptics such as iodine.
2 The skin should be stretched so that it is held taut, and the punch biopsy inserted and gently rotated with firm pressure. The sample will elevate and can then be removed at the base with sharp scissors or scalpel. It should not be crushed as it is removed. A small core of tissue is then obtained. The cervical biopsy forceps should not be used for vulval biopsies as they crush the tissue and do not provide adequate samples (Figure 7.2). Diathermy and other techniques can be used for haemostasis, but not to remove the specimen as the heat artefact makes histological interpretation difficult.
3 The biopsy site can be sutured with an absorbable thin suture (4/0 or 5/0). For shave biopsies, haemostasis can be achieved with the application of silver nitrate.
4 Adhesive dressings are not helpful; a folded piece of soft gauze is adequate, which can be held in place with underwear.
Post‐biopsy instructions
Most biopsies heal well within 5–7 days, and if sutured, the sutures usually absorb in 10 days. For small punch biopsies, analgesia is rarely required, but if needed paracetamol should be used to avoid the increased bleeding tendency of aspirin. Simple instructions given to the patient and backed up with written information should include the following:
Figure 7.2 Example of poor biopsy technique resulting in a crushed specimen, which makes accurate interpretation impossible.
Avoid soaking the area in the bath for 48 hours, but showering is fine. The area should be cleaned daily.
Apply yellow soft paraffin to the area as a barrier before urinating to reduce any discomfort.
Avoid heavy exercise, swimming, or sexual intercourse until the area has healed.
If the area bleeds – apply firm pressure.
Signs of infection include erythema, pain, swelling, discharge, or fever, and then medical advice should be sought.
Samples
The biopsy specimen is immediately put into 10% formalin. If there are multiple biopsies, these must be put into separate pots and labelled correctly. Samples for direct immunofluorescence should be placed in Michel’s medium, which is a useful transport medium with the specimen being stable for 28 days [7]. Direct immunofluorescence (DIF) is used in the investigation of immunobullous disease and detects auto‐antibody/antigen complexes and uses fluorescent labelled antibodies to bind directly to the target antigen in the skin. There are specific immunoglobulins and binding patterns in different immunobullous disease (see Chapter 26).
Specimens for electron microscopy are put into liquid nitrogen or glutaraldehyde.
Documentation
The patient details on the sample pot must correspond to those on the request form. The procedure and instructions given to the patient should be documented. Most departments now use the WHO surgical checklist for this.
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