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Topic 22. Pigmented nevi

Melanocytic naevi (moles)

The term nevus refers to a lesion, often present at birth, which has a local excess of one or morenormal constituents of the skin.

Melanocytic naevi are localized benign proliferations of melanocytes. Their classification is based on the site of the aggregations of nevus cells

Classification:

1. Congenital melanocytic naevi2. Acquired melanocytic naevi

Junctional naevus Compound naevus Intradermal naevus Spitz naevus Blue naevus Atypical melanocytic naevus

Cause and evolution

Cause is unknown. Genetic factor? + sun exposure during childhood Most appear in early childhood Main types:

1. Junctional Dermo-epidermal junction.2. Compound dermis + junctional3. Intradermal all in the dermis

Presentation:

1. Congenital melanocytic naevi Present at birth or appear in the neonatal period Usually > 1 cm in diameter. Color brown to black orblue-black. With maturity, some become protuberant and hairy, cerebriform surface. May carry risk of malignant transformation.

2. Junctional melanocytic naevi Roughly circular macules. Color mid to darkbrown (may vary even within a single lesion) Mostly on the palms, soles and genitals

Congenital naevi

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3. Compound melanocytic naevi These are domed pigmented nodules ofup to 1 cm in diameter. Color: Light or dark brown Most are smooth, larger ones may be cribriform, or hyperkeratotic and

papillomatous; Many bear hairs.4. Intradermal melanocytic naevi

These look like compound naevi Less pigmented and often skin-colored.

5. Spitz naevi (juvenile melanomas). Usually found in children. Develop over a month or two as solitary pink or red nodules of ~1 cm diameter Most common on the face and legs. Although benign, they are often excised because of their rapid growth.

6. Blue naevi So-called because of their striking slate grey-blue color On the limbs, scalp, buttocks and lower back. Usually solitary Rare. Very frequent metastasis Histology intact epidermis, cellular polymorphism, mitoses Complete excision is needed

7. Mongolian spots Pigment in dermal melanocytes is responsible for these bruise-like grayish areas Seen on the lumbosacral area of most Downs syndrome and many Asian and blackbabies. They usually fade during childhood.

8. Atypical Melanocytic nevi syndrome (Clark & Lynch) Numerous nevi (10

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Differential diagnosis of melanocytic naevi

Malignant melanomas Lentiginous. Ephelides (freckles) Epithelial tumors

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Pigmented basal cell carcinoma2. Verrucous with bleeding3. Actinic keratoses4. Seborrhoeic keratoses.

Angiogenic tumors1. Angiokeratoma2. Hemangioma3. Pyogen granuloma4. Kaposi sarcoma5. Glomus tumor

Other tumors or lesions1. Dermatofibroma2. Bleeding3. Tattooo

Complications

Inflammation Depigmented halo (pic) So-called halo naevi, benign, Vitiligo Malignant change extremely rare except in congenital melanocytic naevi

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Should be considered if one of the following is present: Itch, enlargement,increased or decreased pigmentation; altered shape; altered contour;

inflammation; ulceration; or bleeding.

Treatment

Excision is needed when:1. A naevus is unsightly (ugly)2. Malignancy is suspected or3. A known risk is present e.g. in a large congenital melanocytic naevus;4. A naevus is repeatedly inflamed or traumatized.

Seborrhoeic keratoses

Aktinic keratoses