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AlexanderSalava

Naevi (Moles)

Essentials

  • A general practitioner often needs to comment on naevi (moles) or nonspecific skin tumours.
  • The benign nature of a naevus cannot always be ascertained by clinical presentation alone.
  • A biopsy may be taken of almost any skin lesion (e.g. a punch biopsy), but if possible the entire pigmented naevus should be removed with a fusiform (elliptical) excisional biopsy including narrow excision margins.
  • The need for a biopsy is usually based on a change noted in the naevus, a risk assessment by the doctor and the patient's wishes.
  • The histological diagnosis of a lesion suspected to be malignant should be obtained as quickly as possible.
  • Most cases of melanoma Melanoma develop on a previously healthy skin and not on naevi that have undergone a change.

General remarks

  • The great majority of naevi and skin tumours encountered by a general practitioner are benign.
  • Some individuals have an increased number of melanocytic (pigmented) naevi (melanocytic naevi, picture 1); a large number of seborrhoeic keratoses (warts), commonly seen in elderly individuals, is a different condition. The average number of naevi in the Caucasian population is between 20 and 40.
  • The presence of multiple naevi is considered a risk factor for developing melanoma, even though study results are inconsistent and other factors confer a higher melanoma risk.
  • Melanocytic naevi undergo a change over the person's lifetime, and the great majority of slowly changing naevi are benign. New benign melanocytic naevi develop only rarely after the age of 40, and all new pigment changes on the skin that increase in size should be checked visually (as necessary, more frequent monitoring or removal).
  • Benign looking naevi should not be removed just to prevent a malignant progression.

Aetiology

  • The total number of naevi is influenced by genetic factors, and families with multiple naevi are also common.
  • Moreover, lifetime sun exposure can contribute towards the number of naevi. For example, strong sun exposure on fair skin, particularly before puberty, may increase the number of melanocytic naevi and thus indirectly increase the risk of melanoma.
  • See table T1 for the main factors affecting the risk of melanoma.

The main factors affecting the risk of melanoma, based on history and clinical examination. About 330 000 new cases of melanoma were diagnosed worldwide in 2022 http://www.iarc.who.int/cancer-type/skin-cancer/.

History of cutaneous melanomaRisk of new cutaneous melanoma is about 10-fold
Numerous naevi 1
- More than 50 melanocytic naevi
- More than 120 melanocytic naevi		Risk of melanoma
- Approximately 14-fold
- Approximately 19-fold
Occurrence of atypical melanocytic naevi on the skin
  • A single atypical melanocytic naevus occurring on the skin does not increase the risk of melanoma.
  • If there are multiple atypical naevi (especially in atypical moles syndrome, AMS)2 , the risk of melanoma varies between 2 and 1 269 times depending on whether the patient or a close relative has melanoma (Rigel classification)
First-degree close relative with cutaneous melanomaRisk of melanoma is about 2-fold
Very fair skin type (Fitzpatrick classification I-II)3 Risk of melanoma is about 2-fold compared to dark skin type (Fitzpatrick IV)
Lifetime cumulative UV exposure; skin burns, especially in childhood and adolescence; high solarium useIncrease in risk is individual; difficult to assess
  • 1 Numerous naevi refers to an increased number of melanocytic naevi on the skin; and not, for example, to a high number of seborrhoeic keratoses or haemangiomas.
  • 2 In the atypical mole syndrome, the patient has numerous naevi, atypical melanocytic naevi and often a close family history of melanoma (hereditary risk of melanoma).
  • 3 Fitzpatrick classification:
    • I: always burns in the sun, never tans, very pale complexion, freckles, light or reddish hair
    • II: usually burns in the sun, tans poorly, pale complexion, light brown hair
    • III: sometimes mild sunburn, tans evenly, pale or light brownish complexion, dark brown hair
    • IV: very rarely burns in the sun, always tans evenly, light brown complexion, dark hair
    • V: very rarely burns in the sun, tans quickly and evenly, dark brown complexion, dark or black hair
    • VI: never burns in the sun, very dark or black complexion, black hair
Diagnosis
  • Junctional melanocytic naevi are brown lesions at the level of the skin with well demarcated borders (picture 2).
  • Benign intradermal melanocytic naevi are usually less than 1 cm in diameter, are clearly raised from the skin and have a fairly soft texture. They are usually poorly pigmented and are therefore tan or skin coloured (picture 3).
  • A skin lesion should usually be removed or biopsied, at least in the following circumstances:
    • The doctor considers that, based on clinical presentation, the patient's risk factors and/or changes noted in the naevus, it might be malignant.
    • The patient suspects that the lesion is malignant and the suspicion is at least slightly grounded. If a seborrhoeic wart can be confidently identified, there is no need to send it for analysis (can be removed with curettage).
    • The lesion causes functional discomfort, e.g. it rubs against the bra or belt.
  • Signs suggestive of a malignant naevus are:
    • the naevus has clearly increased in size (picture 4)
    • the appearance of a new melanocytic naevus or an existing naevus becoming asymmetrical and uneven
    • a nodule/s developing on the naevus
    • the naevus develops a noticeably uneven colour
    • the naevus is exceptionally large (picture 5).
  • Signs suggestive of malignancy on a melanocytic naevus:
    • a non-healing ulceration of unknown aetiology on the naevus
    • inflammation, pus, crust formation, bleeding, altered sensation, itching and tingling on the naevus. However, these signs do not occur in melanoma until in the late stages.
  • The ABCDE rule (table T2) can be used to assess the indication for naevus removal (especially for early detection of melanoma).

The more factors found in a pigmentary change, the greater the need for removal. Usually two or more factors will justify diagnostic removal.

Shape of the naevusMore detailed description of the shape
A (Asymmetry)Asymmetrical in shape, structure and pigmentation, asymmetry in axis
B (Border)Lesion with poorly defined border, notched edge
C (Color)Multiple colours, varying, different shades, uneven colour
D (Diameter)Diameter greater than 6 mm, large lesion
E (Evolution)Increase or change in lesion, ideally confirmed by measurement or photographs

Differential diagnosis

  • It is important to differentiate melanocytic naevi from other benign skin lesions which have no impact on the patient's melanoma risk and which will never progress into a malignancy.
    • Seborrhoeic keratosis (seborrhoeic warts, “senile warts”, picture 6)
    • Haemangiomas, e.g. cherry angiomas (picture 7)
    • Dermatofibroma (pictures 8 9)
    • Skin tags (fibroma molle, picture 10)
  • Skin lesions that mimic malignancy should also be borne in mind.
    • Eccymosis (for example, on a heel or under a nail)
    • Blue naevus (picture 11)
    • Lentigo (picture 12)
    • Naevus spilus (picture 13)
    • Spitz naevus (pictures 14 15)
    • Pyogenic granuloma (picture 16)

Treatment Differential Diagnosis of Mole and Melanoma

  • The need for a biopsy is often based on the increased size of a naevus, a risk assessment by the doctor and the patient's wishes.
  • Suspicious pigmentary changes should, primarily, be removed entirely with small margins.
  • The naevus is usually removed using a fusiform (elliptical) excisional biopsy with 2-3 mm surgical margins ensuring that some fat tissue is included.
  • A punch biopsy can be taken of any skin lesion. To the extent possible, also with punch biopsy an attempt should be made to remove the lesion completely (choosing a punch slightly larger than the diameter of the lesion).
  • If the lesion is large, a punch biopsy is taken from the most representative place (the darkest or thickest area, for example).
  • Any aesthetic concerns or an awkward position of the lesion should be considered, and therefore the histological diagnosis, for example, of a facial lesion should be confirmed with a punch biopsy.
  • The pathology referral should contain at least the following information:
    • size of the naevus
    • whether a complete removal was attempted or whether it was a biopsy (partial removal by punch or knife).
    • Check also local guidance.
  • A benign melanocytic naevus
    • If the melanocytic naevus turns out to be histologically benign (benign melanocytic naevus), no further excision is required, even if it extends histologically to the margin or if it was a punch biopsy.
  • A dysplactic melanocytic naevus
    • In the case of low grade dysplasia, it is sufficient to have attempted to remove the entire naevus by knife or punch excision; there is no need for further excision.
    • In high grade dysplasia, further excision is performed with a fuciform excision with 5 mm clinical side margins and a depth of penetration down to the fatty tissue.

Prevention and monitoring

  • Very high risk patient groups warrant regular monitoring, and the monitoring of most patients with numerous naevi can take place in primary health care.
  • In risk patients, once a year is a good monitoring interval.
  • The patients should be encouraged to self-monitor their naevi and to take photographs so that these can be compared to see if a naevus has changed.
  • The follow-up is planned individually taking into account the patient's risk factors (in risk patients usually 2 or more of the following are present: increased number of melanocytic (pigmented) naevi, clinically atypical naevi, earlier removal of histologically dysplastic naevi, family history of melanoma, light-coloured skin type and extensive exposure to sunlight, for example through long stay in a sunny country.
  • The development of melanoma may be prevented by sheltering from sunlight, e.g. by using sun screens, protective clothing and a wide brimmed hat.
  • It is particularly important to protect children and adolescents against UV radiation.

Specialist consultation

  • A naevus shown to be malignant or one that is difficult to remove.
  • See Melanoma Melanoma

    References

    • Vuong KT, Walker J, Powell HB, et al. Surgical re-excision vs. observation for histologically dysplastic naevi: a systematic review of associated clinical outcomes. Br J Dermatol 2018;179(3):590-598. [PubMed]
    • Tan SY, Strazzulla LC, Li X, et al. Association of clinicopathological features of melanoma with total naevus count and a history of dysplastic naevi: a cross-sectional retrospective study within an academic centre. Clin Exp Dermatol 2018;43(5):566-572. [PubMed]
    • Martin-Gorgojo A, Requena C, Garcia-Casado Z, et al. Dysplastic vs. Common Naevus-associated vs. De novo Melanomas: An Observational Retrospective Study of 1,021 Patients. Acta Derm Venereol 2018;98(6):556-562. [PubMed]
    • Kim CC, Berry EG, Marchetti MA, et al. Risk of Subsequent Cutaneous Melanoma in Moderately Dysplastic Nevi Excisionally Biopsied but With Positive Histologic Margins. JAMA Dermatol 2018;154(12):1401-1408. [PubMed]