An unusual case of compound naevus of the scalp with hair greying, suggesting melanoma in dermoscopy

Based on clinical and dermoscopic morphology, scalp naevi can be divided into six main groups, namely common, papillomatous, eclipse, congenital, blue and atypical naevi [1]. For the latter, histopathological diagnosis is mandatory to rule out melanoma.
Herein we present a case of an unusual clinical and dermoscopic presentation of a scalp naevus resulting in skin and hair depigmentation.
An 11-year-old girl was referred to our clinic because of a recent onset of hair greying within a pre-existing congenital scalp naevus located in the occipito-parietal region. Moreover, there was a history of slow enlargement and development of the nodular area within the naevus two years before. Clinically, a flat pigmented lesion with grey hair, measuring 5 × 2 cm with three firm white and bluish nodules measuring 5 mm in diameter was seen (Figure 1 A). Grey hair was growing within the entire lesion (Figure 1 B). Dermoscopy revealed a structureless pattern with white and grey colours suggesting melanoma (Figure 1 C). At the periphery some brown globules (clods) were noted. To rule out melanoma arising in the naevus, a biopsy of the nodular area was performed. Histopathological examination revealed a compound naevus with congenital features.
Because of the unusual presentation, the naevus was excised in two steps and histopathology confirmed the diagnosis of a compound naevus. Histopathology revealed an uneven distribution and heterogeneous cellular density of melanocytes with irregular distribution of melanin (intra- and extracellular distribution). Foci of homogenisation of the connective tissue stroma were visible in the upper dermal layers; there were also areas of fibrosis and scarring of the connective tissue stroma deeper in the dermis (mainly around the hair follicles) (Figure 1 D). Melan A immunohistochemistry showed a normal or increased melanocyte count in the stratum basale of the epidermis, and a significantly decreased number of melanocytes or complete lack of these cells in the hair follicles (Figure 1 E). This finding may be considered the cause of the discoloured hairs. Melanin granules were detected through Fontana-Masson histochemical staining (Figure 1 F).
Changes in the pigmentation of naevi located within the scalp may include more intense coloration (physiologically or in the case of malignant transformation), as well as the loss of pigment as in e.g. Sutton naevus, dying naevus, melanoma and during metastatic melanoma...


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