Clinical course of naevus

Melanocytic naevi (moles) are benign proliferations of a specific type of melanocytes called ‘naevus cells’. Mostly they are acquired, only seldomly present from birth (congenital melanocytic naevi). Common acquired melanocytic naevi (banal naevi) are a normal phenomenon. During life, new naevi develop and some will disappear. Especially during childhood and adolescence, enlargement and increasing elevation of naevi are natural processes. 

Sun exposure in childhood, heredity and skin type are factors related to the development of new naevi. The diagnosis is made on clinical appearance. Naevi have a wide variety of appearances but tend to be ≤6 mm in diameter and symmetric with even pigmentation, round or oval shape, regular outline, homogeneous surface and sharply demarcated border. Most acquired naevi remain benign and do not need treatment. They generally do not cause complaints although patients may ask for excision for cosmetic reasons. Naevi are mostly presented to the GP for a check or to confirm their benign character, or to distinguish them from (pre)malignant proliferations. A melanoma, the most serious form of skin cancer only seldomly arises from a common naevus, it mostly appears ‘de novo’. 

The examination of melanocytic naevi considers their shape, colour, symmetry and size and is aimed at distinguishing banal naevi from other types of skin proliferations, especially from melanoma. Atypical naevi are benign acquired melanocytic naevi that share some of the clinical features of melanoma such as asymmetry, border irregularities, colour variability, and diameter >6 mm. The presence of five or more atypical naevi is associated with an increased risk of melanoma. In these cases, a referral to the dermatologist for periodic skin checks is advised.

How are naevi recorded in FaMe-Net?

In ICPC-2, a naevus is coded with S82. 

Epidemiology of naevus in FaMe-Net

The incidence of naevi is 17.5 per 1000 patient years, meaning 17-18 new diagnoses per 1000 patients per year. Women more often present to their GP with a new naevus than men. The incidence is 22.1 per 1000 female and 12.6 per 1000 male patients respectively. Patients in the age group 15 to 44 years most commonly present with a new mole. Link/Figure 1

The prevalence of naevi is 24.0 per 1000 patient years, meaning that among 1000 patients in a year 24 search help from their GP for naevi. Again, the prevalence is highest in female patients and in patients aged 15-44 years. However, ‘a mole’ is a health condition for which GPs provide care to patients from all sex and age categories. Link/Figure 2

The higher prevalence number compared to the incidence number implies that naevi commonly require repeated attention of the GP, i.e. multiple encounters throughout different calendar years in one episode.  

How do patients with naevus present to their GP?

The most common reason for encounter (RFE) for naevus is ‘naevus’. In 54% of all new episodes patients have recognised the irregularity as a mole and present it as such. Patients also commonly present to the GP with the request to check their skin (*31). In 5% patients present with a request for excision/removal of the naevus. Link/Table 3 With increasing age, the first and second most common initial RFEs (‘naevus’ and ‘request for skin check’) gradually change positions. The ‘age range’ can be altered to see RFEs in different age groups. Link/Table 4 

Of all episodes starting with RFE ‘naevus’, the final diagnosis was indeed ‘naevus’ in 75%. Link/Table 5 This means that the condition is easily self-diagnosed.

How do FaMe-Net GPs act?

Common interventions in episodes of naevus are referral to the specialist (in 18%) and excision by the GP (in 17%). These percentages may be higher than expected. This might be due to some underreportion of naevi not requiring intervention if patients present with multiple problems in a consultation and finally ask for a naevus check. Histologic examination is recorded in 9%, exclusively after surgery by the GP. These are percentages per year. Link/Table 6 Specialist referrals are usually to the dermatologist, sometimes to the plastic surgeon, and seldomly to the surgeon or ophthalmologist. Link/Table 7 No obvious sex differences were observed in the interventions for naevi. Referral to the specialist was slightly more common (21% per year) in patients aged 45-74. Link/Table 8 Excisions by the GP were uncommon in children, and generally absent in the youngest (0-4) children. Link/Table 9

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