With some clinical presentations, the diagnosis can be made on the basis of the history and examination alone. However, investigations may be necessary to confirm the clinical diagnosis and to gain further information in order to formulate an appropriate management plan. These investigations need to be tailored to the clinical features, as performing extensive investigations without a clinical differential diagnosis is never helpful.
With any investigation, there must be good communication with the laboratory and the appropriate specialist, particularly with the histopathologist as clinicopathological correlation is crucial. If infection is suspected, special tests are often required, which may need specific collection techniques and transport media. This will require discussion with microbiology specialists and the local laboratory before taking specimens.
Biopsy
Reasons for taking a biopsy
A vulval biopsy is performed to confirm the clinical diagnosis, to help when there are a number of clinical differential diagnoses, or where the clinical features are atypical. A biopsy must always be done in the context of clinical diagnosis, and if sent in isolation without this, it is very easy to draw the wrong conclusion. The majority of biopsies are done for diagnostic reasons, but excisional biopsies can also be therapeutic.
Site of biopsy
In order to get the most useful information from the biopsy, the site must be carefully chosen. In general, the edge of a lesion will give the most helpful histological information. The base of an ulcer or erosion is more likely to be non‐specific (Figure 7.1). If there is widespread change, with non‐uniform features, such as in extensive intra‐epithelial disease, multiple mapping biopsies may be required. These must be labelled correctly so that correlation with the original biopsy site is clear.
Most vulval biopsies are easily performed under local anaesthesia in the outpatient setting, but it is best to avoid biopsies of the clitoris, urethra, and anal margin. These patients should be referred to the relevant specialist – gynaecologist, urologist or colorectal surgeon – to consider biopsy under general anaesthetic.
Pre‐biopsy
A clear drug history specifically asking about anticoagulants must be taken before the biopsy. Some patients may take low‐dose aspirin that is not prescribed, so this needs to be checked. Genetic clotting problems and allergies, especially to local anaesthetic, must be detailed.
The procedure is explained and written informed consent 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
