Zlatko Marusic and Eduardo Calonje Naevi are relatively uncommon on the vulva, but when they do occur, they may have atypical features. Both melanocytic and epidermal naevi are discussed in this chapter. Vulval naevi are seen in about 2% of pre‐menopausal women [1]. Melanocytic naevi of the intradermal, compound, and junctional types occur on the vulva, but the important variant is the atypical genital naevus, which can be mistaken for melanoma. Although additional investigations such as dermoscopy may help in differentiating vascular from pigmented lesions, it is generally recommended that pigmented lesions should be excised for histological assessment. Good clinicopathological correlation and expert dermatopathology review are important when diagnosing vulval pigmented naevi as the management and prognosis depend on accurate diagnosis. Naevi can also coexist with lichen sclerosus, and both clinically and histologically, these lesions may mimic melanoma [2, 3]. These lesions occur in younger women and have atypical clinical and histological features [4–6]. They are important to recognise in order to prevent unnecessary treatment for the mistaken diagnosis of melanoma. BRAF V600E mutations have been demonstrated in AGN but not in melanoma [7, 8]. AGN are usually seen on the inner labia majora or minora and are often irregular, sometimes with ill‐defined margins (Figure 39.1). They can be difficult to distinguish clinically from melanoma, and excision is recommended [9]. Dermoscopy may be of help in diagnosis [10], but histology is the gold standard in diagnosis, and the lesions should be reviewed by an expert dermatopathologist. Most AGNs are symmetrical, well‐demarcated, and composed of large epithelioid (or sometimes spindled) melanocytes with retraction artefact or cellular discohesion within the junctional component. Their appearance may be worrisome on low power due to their size, cellularity, and occasionally striking pigmentation. Cytological atypia may be present and tends to be variable. Nests of tumour cells show variation in size or shape and may show confluence and a parallel arrangement with regards to the epidermal‐dermal junction (Figure 39.2). Melanocytes in these lesions contain eosinophilic cytoplasm and a single nucleolus. Focal upward migration may be seen. A band of dense eosinophilic fibrosis is not uncommonly seen in the superficial dermis. A dermal component is often present and consists of variably sized intradermal melanocytic nests. Mitotic figures are exceptional and if present are noted superficially. Hair shafts and sweat gland ducts are commonly involved. However, as noted previously, there is an overall symmetry with cellular maturation in the deep dermis. Figure 39.1 Atypical genital naevus. Irregular dark naevus on right labium majus. Excision is needed, but there is no evidence that they are precursors of melanoma [5]. Blue naevi usually present in childhood, and rare examples are described on the vulva involving the labia in an adolescent [11] and the clitoris in another case [12]. One case of late metastatic disease is described where a vulval blue naevus excised in childhood presented with ovarian metastases 15 years later [13]. This has been described as a distinct variant of giant congenital melanocytic naevus [14], which can be mistaken for melanoma. The lesions are usually present at birth and can grow to a very large size. They are often associated with large congenital melanocytic naevi affecting the lower abdomen and thighs [15, 16]. The large size can cause problems with gait, and one case associated with intractable pruritus eventually responding to ondansetron is reported [17]. There is a very deep involvement of the dermis by naevus cells, which are partially distributed in a single cell (the so‐called string of pearls) pattern with a focal appearance reminiscent of neural structures (Wagner‐Meissner bodies). Treatment is with excision.
39
Benign Vulval Naevi
Benign melanocytic naevi
Atypical genital naevi (AGN)
Genetics
Clinical features
Histological features
Management
Blue naevi
Bulky naevocytoma of the perineum
Clinical features
Histological features
Management
Inflammatory linear verrucous epidermal naevus
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
