Junctional melanocytic nevus

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Junctional melanocytic nevi

Key Points

  • Junctional Nevi are a sub-class of Common Acquired Melanocytic Nevi
  • Typically they are light to dark brown macules, 1-10 mm in diameter, and located on sun exposed areas such as the trunk.
  • Junctional Nevi are benign proliferations of melanocytes in the epidermis.
  • Common finding in all people, however increased numbers of nevi increase risk for developing melanoma 

Junctional Nevi are clusters of melanocytes that develop within the superficial layer of skin, the epidermis. They appear as slightly elevated papules or macules, usually with a diameter <6mm.  Junctional nevi are typically circular with regular borders and their coloring varies from tan to brown to black.

There are three types of common acquired melanocytic nevi; Junctional nevi, Compound Nevi, and Intradermal Nevi. Junctional nevi are the first type of melanocytic nevi to appear and are usually visible in early childhood. Most junctional nevi will “mature” through adulthood and lose their pigmentation.  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 skin they begin to lose their ability to produce pigmentation (melanin). For example, intradermal nevi should have less pigment and more closely resemble the color of flesh because they deeper in the skin.  This loss of pigment, in a general sense, also aligns with the age in which these different nevi first appear; Junctional nevi in early childhood, compound nevi in childhood to early adulthood, and intradermal nevi by the third or fourth decade. In childhood, junctional nevi may appear anywhere on the body especially sun exposed areas such as the legs, neck, head, and trunk. In adulthood, they are more likely to appear on the palms, soles, and the genital region. Junctional nevi that appear in late adulthood are at increased risk for being malignant. Individuals with lighter skin typically have more junctional nevi and there is no difference in their prevalence between the sexes.

Differential diagnosis

  •          Congenital Nevus
  •          Melanoma
  •          Café’-au-lait macule
  •          Lentigo Maligna
  •          Atypical Nevus
  •          Solar Lentigo
  •          Seborrhoeic Keratosis
  •          Acanthoma

 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.

 

Treatment

Key points

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

Junctional Nevi are, by definition, benign and most 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, chronic irritation, cosmetic concerns, or a change in the size, shape, or pigmentation of the mole are reasons that a junctional nevus to 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

  1. Rooks Textbook of dermatology
  2. Clinical Dermatology
  3. General Dermatology
  4. www.emedicinemedscape.com
  5. www.up-to-date.com
  6. www.dermnetz.org
  7. www.ncbi.nlm.nih.gov