part of the normal anatomy. They are very prominent in some women but can be seen more clearly if the labia are stretched (Figure 2.3).
The clitoris
The clitoris is a complex structure, and our understanding of the anatomy has been helped by the use of MRI studies [15,16].
The clitoris has a wishbone like structure with the arms being the crura extending forwards as the corpora cavernosa and meeting in the midline to form the body of the clitoris (Figure 2.4). The tip of the body then bends anteriorly to form the glans clitoris, which is the only visible part, and is non‐erectile. The glans is covered by the clitoral hood, formed by the anterior fusion of the labia minora. The crura are attached to the pubic rami and covered by the ischiocavernosus muscle, and the clitoral body is attached to the pubic symphysis by a suspensory ligament. The clitoral bulbs lie between the crura and the urethra against the vaginal wall. They are covered by the bulbospongiosus muscles, which extend from the perineal body, around the vagina and urethra, to the glans clitoris. The whole of the clitoris is composed of similar erectile tissue with the exception of the glans [16].
Figure 2.2 Variation in appearance of normal labia minora. (a) Symmetrical labia minora with pigmentation on rim. (b) Labia minora protruding outside labia majora in a patient with lichen sclerosus. (c) Fimbriation and pigmentation on rims of labia minora. (d) Asymmetry of labia minora with bifid insertion on right side.
The average clitoral width in children was measured at 3.8 mm, and this did not alter with age although the other vulval components increased with age [9]. This is important to exclude clitoral hypertrophy. In an adult study, the clitoral width was reported to increase with parity [17], but this has not been confirmed in larger studies.
The vestibule
The vestibule extends from the clitoral frenulum to the fourchette and laterally from the hymenal ring to a variable position on the inner aspect of each labium minus. The vagina, urethra, ducts of Bartholin’s glands, and the minor vestibular glands all open into the vestibule. The area of the vestibule between the vaginal opening and the posterior union of the labia minora forms a shallow depression termed the vestibular fossa or fossa navicularis. Scars from obstetric tears can be seen on the anterior and posterior vestibule and sometimes pigment.
Figure 2.3 Fordyce spots: yellow papules on inner labium majus.
Figure 2.4 Anatomy of the clitoris.
Hart’s line
In some patients, there may be a very distinct line which represents the transition from the keratinised skin of the labium minus to the vestibular mucosa. This was first described by the Edinburgh gynaecologist David Berry Hart in his textbook of gynaecology in 1882 [18] and is termed ‘Hart’s line’. He wrote ‘a line running separates mucous membrane from skin – starting at the base of the inner aspect of the right labium minus, it passes down beside the base of the outer aspect of the hymen, up along the base of the inner aspect of the left labium minus, in beneath the prepuce of the clitoris and down to where it started from’. This is often very obvious, particularly in young women, and the normal mucosal surface medially is frequently mistaken for inflammation (Figure 2.5).
Bartholin’s glands
Bartholin’s glands are situated deeply in the posterior labia majora. They lie just inferior and lateral to the bulbocavernosus muscle and are normally not palpable. The main duct of each Bartholin’s gland passes deep to the labium minus to open into the vestibule, and their openings are often seen at 5 and 7 o’clock. These can be very prominent in some patients with erythema around the glandular duct opening (Figure 2.6).
Figure 2.5 Hart’s line, which demarcates the junction of the keratinised skin of the labia minora with the non‐keratinised mucosa of the vestibule.
Figure 2.6 Openings of Bartholin’s ducts.
Minor vestibular glands
The minor vestibular glands are small shallow glands usually less than 3 mm into the dermis and open directly to the surface. In postmortem studies, they vary in number from 1 to more than 100 [19].
Vestibular papillomatosis
Vestibular papillae are 1–5 mm thin projections that occur in the vestibule and inner labia minora, and are a normal variant (Figure 2.7). It is suggested that they are the female equivalent of the tiny symmetrical projections found around the coronal sulcus known as penile pearly papules of the penis [20]. Originally, it was thought that the lesions were induced by the human papillomavirus (HPV), but there is now good evidence to the contrary [21, 22]. The normal glycogenation of the cells at the vestibule is often mistaken for koilocytosis, which is another reason for good communication with the pathologist.
Vestibular papillae can be distinguished from viral warts as they are soft and the same colour and texture as the surrounding mucosa. They are symmetrical in distribution and each papilla arises from a solitary base (Figure 2.8), whereas viral warts often coalesce into a single base. Dermoscopy has also been used to distinguish the two entities [23] where the single base of each papilla is again confirmed. The application of 5% acetic acid does not produce acetowhitening in vestibular papillomatosis. They are usually asymptomatic, and no treatment is needed.
Figure 2.7 Vestibular papillae. Multiple filiform projections of the vestibular epithelium.