Intradermal Melanocytic Nevus

Intradermal nevi

Key points

Intradermal Nevi are a sub-class of Common Acquired Melanocytic Nevi.
They are typically skin colored or tan, dome shaped papules less than 1 cm in diameter.
Intradermal Nevi are benign proliferations of melanocytes in the dermal layer of skin.
Intradermal nevi are a common finding in man people, however a change in color, shape, or size should be investigated for malignant transformation.

Intradermal nevi are nests of melanocytes found in the dermal layer of skin. Intradermal nevi are typically raised, dome shaped papules less than 10mm in diameter. These lesions are well demarcated and have a soft, rubbery texture. They lack pigment, therefore they are skin colored or tan, and may contain brown flecks or telangiectasias (small dilated blood vessels). They may also contain 1-2 terminal (mature) hairs or pseudo-horn cysts (collections of keratin) that are more commonly seen in seborrheic keratosis. Intradermal nevi are typically not seen until the third decade and may appear on the face, head, scalp, neck, trunk or extremities. Older intradermal nevi that appear on the trunk or flexures may become pedunculated (elongated tissue) similar to skin tags.

There are three types of common acquired melanocytic nevi, Junctional nevi, compound Nevi, and intradermal Nevi. As we age, melanocytes migrate down through the layers of the skin starting with the epidermis, down to the epidermal-dermal junction and finally into the dermis. This creates an evolution of the nevi from junctional to compound to intradermal. As melanocytes move down through the layers of skin they become less active and produce less pigment (melanin). Intradermal nevi should have the least amount of pigment and resemble the color of flesh because they are deeper in the skin. This loss of pigment, in a general sense, also aligns with the age in which these different nevi appear; Junctional nevi in early childhood, compound nevi in childhood to early adulthood, and intradermal nevi by the third or fourth decade.

Differential Diagnosis

Basal Cell Carcinoma

Neurofibroma

Trichoepithelioma

Sebaceous Hyperplasia

Dermatofibroma

Acrochordon

Verruca

Nodular Melanoma

Clear Cell acanthoma

Appendageal tumors

Diagnosis

Key points

Clinical presentation is the most important aspect of diagnosis
Histologic examination confirms diagnosis

Diagnosis is primarily made by history and clinical presentation. When the clinical picture is murky, a complete excisional biopsy and histopathologic evaluation of the mole is made to rule out melanoma. The histologic findings of small, uniform, symmetrical, well circumscribed nests of melanocytes are reassuring for melanocytic nevi.

Due to their decreased activity, malignant transformation of intradermal nevi is extremely rare. Because they are skin colored, intradermal nevi with telangiectasias are often confused with basal cell carcinoma prior to histologic examination. Likewise, inflammation or infection of a hair follicle in an intradermal nevus may cause alarm in patients for fear of malignancy. However, these changes usually occur acutely and are rarely related to malignant transformation.

Treatment

Key points

In most cases, moles do not require treatment
Suspicious moles should be removed and examined
Prevent skin damage from sun exposure

Melanocytic Nevi are, by definition, benign and most moles remain benign throughout a person’s lifetime. Therefore, most moles will never need to be treated. However, suspicion that a mole may be a melanoma, a change in the size, shape, or pigmentation of the mole, chronic irritation, or cosmetic concerns are reasons that the melanocytic nevi may be removed via excisional biopsy. When this is performed, if possible, the entire lesion should be removed and undergo histologic evaluation to rule out malignancy.

It is important for individuals who have a significant number of nevi to have counseling about the dangers of excessive sun exposure, skin protection, and to undergo periodic total skin inspections by a dermatologist.

References

Rooks Textbook of dermatology
Clinical Dermatology
General Dermatology
www.emedicinemedscape.com
www.dermnetnz.org
www.ncbi.nlm.nih.gov