History
A 49-year-old woman presents with a 20-year history of a nodule on her face, which she felt had slowly increased in size over the years. She is anxious about the lesion as friends and neighbours have starting asking her what it is. She feels embarrassed by the lesion and is keen to have it removed. There is no history of itching or bleeding of the lesion. She has quite fair skin (Fitzpatrick type II) and has had limited sun exposure.
Examination
She has a dome-shaped, firm, flesh-coloured nodule lateral to her left eye (Fig. 59.1). There is no surface change felt over the nodule, no telangiectasia and no tenderness. Full skin examination does not reveal any other lesions of note.
Questions
• What is this lesion?
• Can you classify this lesion on clinical grounds?
• How would you manage this patient?
Medicine
This nodule is a benign intradermal naevus, otherwise known as a ‘mole’. A naevus from the word ‘nest’ is a benign proliferation of cells, as in this case melanocytes. Naevi may be congenital or acquired and may contain melanocytes, epidermal cells or connective tissue.
Melanocytic naevi are very common and are usually multiple. Naevi may be macular or papular/nodular, they vary in colour from pink or flesh-coloured to dark brown or black.
Most are round or oval in shape. They are usually 1 cm in diameter and are common in patients of skin types I–IV and less common in types V and VI.
Melanocytic naevi are classi-fied accordingly to their his-tology. They are described according to the site of the nae-vus cells in the skin (Fig. 59.2).
The naevus cells in melano-cytic naevi are thought to be derived from melanocytes that migrate to the epidermis dur-ing embryonic development from the neural crest.
Melanocytic naevi begin as a proliferation of cells along the dermo-epidermal junc-tion, forming a junctional naevus. Clinically these moles tend to be flat and dark brown (Fig. 59.3). With continued proliferation, cells extend from the dermo-epidermal junc-tion into the dermis, forming nests of naevus cells, so-called compound naevus. Clinically these moles have a centrally raised area and may be surrounded by flat pigmentation (Fig. 59.4). Finally, the junctional compo-nent of the naevus may resolve leaving an intradermal naevus, as in this patient.
These moles often protrude from the skin surface and are flesh-coloured or slightly pigmented.
Acquired melanocytic naevi appear through-out childhood and adolescence reaching a peak in early adulthood. They may also appear in later adult life, usually secondary to excessive ultraviolet light exposure for the skin type. In the 60th decade onwards naevi usually gradually involute and many disappear altogether. This patient should be reassured that her mole is benign. She should be given sun-protection advice as she has fair skin and is liable to get sunburn in strong sunlight. Acquired moles should be distinguished from congenital melanocytic naevi (CMNs), which are usually present at birth or appear in the first year of life. Approximately 1 per cent of Caucasians are affected. The lesions are usually 1 cm in diameter and can become protuberant and hairy in nature with increasing age. CMNs usually grow in proportion to the child – sudden increase in growth, satellite lesions appearing at the periphery or nodules forming within them warrant a skin biopsy. The risk of malignant transformation (melanoma) is thought to be very low but is more often reported in so-called ‘giant naevi’ which are 20 cm in diameter.
KEY POINTS
• A naevus is a benign proliferation of melanocytes.
• Naevi can be junctional, compound or intradermal.
• Naevi are either congenital or acquired.
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