ACQUIRED MELANOCYTIC NEVI

Acquired melanocytic nevi, nevus cell nevus, pigmented nevus - acquired melanocytic nevi usually appear in childhood, adolescence or early adulthood. They are the most common skin growths; an adult Caucasian have more than 20-25 such changes on average.

Acquired marginal nevi (junctional nevi) are usually early lesions, appearing in the form of brown spots of varying colour intensity. Some of them remain unchanged but the majority develop into a histologically compound nevi or a skin lesion of a nodular appearance. These include: junctional nevi, skin moles, compound nevi and other distinctive forms.

Junctional melanocytic nevus, marginal melanocytic nevus (naevusmarginalis), pigmented epidermal nevus (naevuspigmentosusepidermalis) - flat, relatively small, brown (usually dark) spots of various shapes. In older age some of them may fade away. The development of nevi  is associated with excessive exposure to sunlight. Location: All over the body surface.  Treatment: Junctional nevi are not susceptible to malignant transformation. They can be removed surgically for cosmetic or preventive indications, if located in areas exposed to irritation (by collar, bra strap, belt, etc.) or if the lesion is subject to rapid change (enlargement, colour change, the occurrence of itching or pain). The most commonly used excision technique is a spindle-shaped, full-thickness excision along the so-called Langer’s lines with a margin of 1-2 mm.

Dermal melanocytic nevus, intradermal nevus, nevus cellularis, pigmented nodular nevus – Clinical picture: Soft papules or nodules, skin-coloured, brown or black, with smooth or papillary surface, sometimes hairy, often pedunculated. The lesions do not undergo malignant transformation. Sometimes a coexistence of nevus and epidermal cysts is observed. Location: Anywhere on the body but most frequently on the face and scalp. Treatment: For cosmetic reasons nevi can be removed surgically by a spindle-shaped, full-thickness excision or a tangential excision, possibly followed by electrocoagulation of the base. It is recommended to remove the nevi exposed to constant irritation.

Compound melanocytic nevus, nevus composituus – A slightly raised lump or nodule in various shades of brown, with smooth or papillary surface. Coloration is typically uneven, usually darker in the centre. Location: Anywhere on the body. Treatment: Surgical removal may be recommended for aesthetic or functional reasons, e.g. in the case of constant irritation by clothing.

Among the acquired melanocytic nevi numerous varieties may be distinguished: Sutton, Mayerson, cockade, Spitz, Reed, blue, acral and  atypical (Clark) nevi.

Sutton’s nevus (naevuspigmentosus Sutton), halo nevus (leukoderma acquisitumcentrifugum) – Clinical picture: A quite frequently occurring round or oval brown nevus surrounded by a ring of depigmentation, usually observed in young people. The occurrence of a Sutton’s nevus in older age requires histopathological examination to exclude melanoma. The depigmented ring is a manifestation of immunological activity associated with the presence of circulating anti-melanocyte antibodies, CD8 T-cells and antigen-presenting cells in the local inflammatory infiltration. The nevus tends to regress spontaneously. The pigmented part loses pigment and the resulting vitiligo lesion is gradually filled with pigment. This process takes on average from several to up to twenty months. Location: Anywhere on the body. Treatment: If the perceivable transformation of the nevus disturbs patients, they should be assured of the benign nature of the lesion.

Meyerson’s nevus (naevuspigmentosus Meyerson) – Clinical picture: A relatively rare pigmented nevus accompanied by the acute local inflammatory response of an eczematous nature. The surrounding area is erythematous, with flaky surface, as in the eczematous changes. Such reaction may be associated with a cell-mediated immune response. Nevi usually occur in children and young people and show no tendency to regress. Lokalizacja: Anywhere on the body. Treatment: The clinical picture may raise patient’s concerns for possible malignant transformation. Steroids applied topically help to control the inflammatory process. If the inflammation persists, the lesion should be excised.

Cockade nevus (naevusencockarde) – Clinical picture: A rare, flat, oval nevus, 8-15 mm in diameter, with light brown, pinkish or dark brown centre and a conspicuous dark reticular ring (resembles a rosette or a bullseye – a targetlike appearance). Nevi are often multiple. Treatment: Despite the unusual appearance, the nevus is not susceptible to malignant transformation. Excision is not necessary, unless there are doubts raised in the differentiation with a dysplastic nevus or a melanoma.

Spitz nevus, juvenile melanoma, spindle and epithelioid nevus – Clinical picture: An uncommon, domed nodule of cohesive consistency and a smooth surface, up to 1.5 cm, reddish-brown or pink-bluish. The nevus usually develops in childhood or adolescence but may occur in later years as well. The nodule grows quickly (within a few months) until it reaches the final size. The nevus usually occurs as an isolated lesion, but minor satellite lesions may develop. There is no risk of malignancy. Location: Face, less frequently neck and lower limbs, with the presence of melanocytes of the epithelioid cell type concentrated along the basement membrane. Treatment: Surgical removal of the lesion. If the clinical or histological picture is diagnostically ambiguous, excision with a margin of healthy tissue is recommended.

Pigmented spindle cell nevus (Reed) – Clinical picture: The growth of a homogenous dark brown colour, flat or flat-topped, with a diameter not exceeding 1 cm, rapidly developing, mainly on the limbs and rarely in other locations. Dermatoscopic image shows characteristic, numerous peripheral streaks with branches, forming a starbust pattern. Due to the rapid growth  and dark colour, melanoma is often suspected. According to some sources, the pigmented spindle cell nevus is a variation of Spitz nevus. Treatment: Surgical excision with a small margin.

Blue nevus (naevuscoeruleus) – Clinical picture: A common, domed, bluish nodule with a diameter of 0.5 cm. The nevus is present at birth or appears later in life. Rare cases of melanoma transformation have been reported. Location: Anywhere on the body. Treatment: Excision with a small margin.

Acral nevus (melanocytic acral nevus with intraepidermal ascent of cells, MANIAC) – Clinical picture: Located on the plantar and palmar surfaces, reflects the shape of the friction ridges, often asymmetrical.

Dysplastic nevus, atypical mole syndrome, Clark’s nevus, atypical nevus, dysplastic nevus syndrome (DNS), nevus with architectural disorder (NAD) – a single dysplastic nevus occurs frequently (in 5% of population), whereas dysplastic nevus syndrome, consisting of multiple dysplastic nevi, is a relatively rare disease entity, which usually runs in families and may turn into melanoma, hence its less frequently used name - familial atypical multiple mole melanoma, FAMMM). Clinical picture: a dysplastic (atypical)  nevus is an acquired pigmented lesion, atypical in terms of clinical picture and histological structure. There are various descriptions of these lesions, for example, according to Dutch Working Group, their characteristic features include: size exceeding 5 mm, fuzzy borders, asymmetry, irregular pigmentation, reddish colouration; according to other descriptions the lesions are dark brown or black. They are usually flat, but sometimes raised in the centre (like a fried egg). The surrounding skin may be inflamed. Most often, these nevi occur during puberty, in young adults and women during pregnancy but rarely in children. The most prominent features of dysplastic nevus syndrome (DNS) according to Newton, include the occurrence of:

  • more than a hundred nevi of a diameter exceeding 2 mm;
  • at least two large atypical moles, histologically confirmed;
  • at least one nevus on the buttocks or two on the dorsal feet;
  • at least one nevus on the scalp;
  • more than one iris nevus.

Confirmation of three or more of the above-listed features (or, if the last criterion is excluded, more than two features) establishes the diagnosis of dysplastic nevi.

This syndrome is associated with an increased risk of melanoma, especially if the patient or patient’s family member suffered from melanoma in the past. Location: Isolated dysplastic nevi may occur anywhere on the body. In the course of dysplastic nevus syndrome, lesions are usually located on the back, chest, abdomen and scalp.

Differentiation: Atypical nevi should be differentiated from melanoma, which is diagnosed on the basis of the existence of pagetoid cells, severe atypia and an inflammatory reaction with lack of melanocytic maturation. If histological evaluation proves complicated, an immunohistochemical examination may help.

Treatment: A single dysplastic nevus should be examined periodically or removed surgically by a full-thickness excision with a margin of a few millimetres and a layer of subcutaneous tissue, with the long axis of the incision directed towards the nearest lymphatic runoff (to facilitate a possible sentinel node biopsy). In patients with dysplastic nevus syndrome dermatological check-ups should be carried out regularly every 6 months. It is also important to collect medical record on cases of melanoma in the family. It is advisable to keep photographic documentation of nevi, preferably computer-stored, for the sake of a development analysis. Lesions with a disturbing clinical picture (sudden enlargement, inflammation, disintegration followed by ulceration) should be immediately removed and examined histologically. It is advisable to avoid exposure to sunlight and to use sunscreens.