4 The vulva has both keratinized and nonkeratinized (mucosal) epithelium. On the labia majora, mons pubis and perineal region, the epithelium is keratinized and is similar to skin at other body sites. The keratinocytes move upwards through the epidermis and are eventually shed. Four distinct layers can be seen in the epithelium – from bottom to top, basal layer, stratum spinosum, stratum granulosum and, most superficially, the stratum corneum. Skin appendages at these sites include hair follicles, eccrine glands (producing odourless and colourless sweat), apocrine glands (producing a milk‐like odourless secretion, which, due to bacterial action, can release pheromones) and sebaceous glands (Figure 4.1). These appendageal structures vary in their localization. The skin covering the outer surfaces of the labia majora is rich in hair follicles, sebaceous glands, eccrine and apocrine glands. The inner surface has no hair follicles or apocrine glands but several sebaceous glands and some eccrine glands (this is the only region apart from the nipples where sebaceous glands are found without hair). The absence of hair allows the sebaceous glands to be visible to the naked eye and present clinically as slight yellow bumps, called Fordyce spots (see Chapter 1). Figure 4.1 Histopathological features of the normal vulva. The epithelium that covers the hymen, vestibule and inner surfaces of the labia minora is a nonkeratinized mucosal type. Adnexal structures are absent but sebaceous glands are common on the labia minora. Sometimes pigmentation, due to an increase in the number of melanocytes with a high quantity of melanin, occurs on the outer surfaces of the labia minora and on the clitoral hood. The vestibular mucosa is rich in glycogen and it is important not to confuse this with koilicytosis seen with human papilloma infection. Three other types of cells are present in the epithelium. In approaching the diagnosis of a patient with a vulval disorder it is necessary for the clinician to know the terms that are used to describe the cell types and histopathological features of the disease, in order to achieve clear communication with the pathologist. Tables 4.1 and 4.2 contain glossaries of the principal terms used in the pathological description, and some of the more common special stains used to confirm a diagnosis. Table 4.1 Glossary of cell types and structures. Table 4.2 Glossary of histopathological terms.
Basic Histology of the Vulva
Commonly seen in
Basement membrane
Junction between epidermis and dermis
Can be visualized with PAS stain
Epidermal giant cells
Multinucleate keratinocytes
Herpes virus infection
Epithelioid cells
They look similar to keratinocytes with large nuclei and abundant cytoplasm.
Most commonly seen as macrophage‐derived in granulomas
Giant cell
Macrophages with many nuclei as they are formed after ingestion of substance
Seen in foreign body reactions and some granulomatous disease, e.g. ano‐genital Crohn’s disease
Histiocyte
Macrophages derived from monocytes involved in phagocytosis
Have larger nuclei and more abundant cytoplasm than lymphocytes
Keratinocyte
Epidermal cell
Macrophage
A cell derived from the bone marrow that is involved in phagocytosis.
Plasma cells
The nucleus is eccentric and stippled while the cytoplasm is pale
Common in vestibule as a normal finding
Zoon’s vulvitis, syphilis
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