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need to tell the pathologist?

      Clear clinical details must be given to the pathologist, which should include clinical features and the differential diagnosis. It is most helpful to supply them with a clinical photograph or diagram detailing the site of the biopsy. They also need to know whether topical treatment has been used and whether EMLA® was applied before the biopsy. As most vulval disease is dermatological, expert dermatopathological review is helpful. A multidisciplinary approach with clinicopathological correlation should be routine practice.

Cytology

      The use of cytological techniques in the diagnosis of vulval disorders is limited, with conflicting results reported in studies. Poor correlation of vulval Pap smear cytology with subsequent histological analysis of neoplasia has been reported [8], but the specificity and sensitivity may be increased with the use of a scalpel technique [9]. Vulval brush cytology may be useful as a triage technique for deciding which patients may require a biopsy for clinically suspicious lesions [10]. Histological examination of a tissue sample should always be regarded as the gold standard.

      However, for a rapid diagnosis of herpes simplex infection, a Tzanck smear is helpful.

Microbiological investigation

      Swabs

      Swabs can easily be taken for bacterial and yeast culture. A different swab put into transport medium is needed for viral cultures. If a sexually transmitted infection is suspected, the patient should be referred to a genitourinary medicine clinic for full investigation, screening, and contact tracing.

Scrapings

      If a fungal infection is suspected, skin scrapings will be needed. These can be taken with a broad ‘banana’ blade and the edge of a scaly lesion gently scraped. The scrapings are collected on to a dark paper package for transport to the laboratory. If there is extensive involvement of a hair‐bearing area or a deep fungal infection is suspected, culture of a biopsy taken into a dry pot is helpful.

Serology

      Serology may be needed to confirm some infectious diseases (see Chapter 9–20).

Wet mount microscopy

      This is a simple technique used in the investigation of vaginal discharge. A sample taken and placed in normal saline or 10–20% potassium hydroxide gives rapid results and is particularly helpful in assessing lactobacilli [11].

Wood’s lamp examination

The Wood’s lamp is a device that emits ultraviolet rays but includes a filter of barium silicate to exclude visible light. It is easy to use but is much less reliable in darker skin types because of the high levels of melanin present. It requires a completely dark room, and it is important to remember that false positive results can be achieved with scales, soap, residual topical treatment, or dressings. It can be helpful in diagnosis for a variety of dermatological diseases and infections [12]. It is also used to delineate the margins of lesions to be treated with photodynamic therapy after the 5‐ALA cream is applied (see Chapter 8). The conditions that are relevant to the vulva and the results expected are shown in Table 7.1.

Patch testing

      Patch testing is a measure of delayed type (type IV) hypersensitivity and is used to investigate a suspected allergic contact dermatitis (see Chapter 22). It is of no value in the investigation of urticarial (type I) reactions.

Small amounts of allergens in suitable concentration are placed on aluminium discs or small plastic trays (Figure 7.3) and applied to the back of the patient (Figure 7.4), and then securely attached with hypoallergenic tape. These are removed and read at 48 hours, and then read again at 96 hours after application. A positive test results in an eczematous reaction at the site of application (Figure 7.5).

Table 7.1 Uses of Wood’s light in vulval disease.

Disease	Fluorescence colour
Vitiligo	Bright white
Infections
Pseudomonas	Green
Erythrasma	Coral‐red
Tinea capitis – Microsporum species	Bright green
Tinea capitis – Trichophyton schoenleinii (Note: Other trichophyton species do not fluoresce)	Blue
Pityriasis versicolor	Copper‐orange

Figure 7.3 Allergens for testing placed in plastic trays.

      There are standard series that are used in all patients undergoing patch testing, but it is important to extend these for investigation of an anogenital dermatosis. Patients should be referred to a contact dermatitis clinic so that multiple series to include preservatives, fragrances, medicaments, and topical steroids are tested, otherwise relevant allergens may be missed. It is also helpful to test the patient’s own products that have been used, but these may require dilution to avoid severe irritant reactions. Education on sources of any relevant positive allergens is then provided so that they can be avoided in future.

Resources

      Recommended patch testing series and patient information leaflets

Figure 7.4 Allergens applied to the patient’s back.

Figure 7.5 Positive reaction showing eczematous reaction at the site of application.

       https://cutaneousallergy.org/resources/recommended‐series/

      Patient information about patch testing

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