Junctional nevus

by Allison Osmond MD FRCPC and Archan Kakadekar MD
December 9, 2024


A junctional nevus is a non-cancerous skin tumour made up of specialized cells called melanocytes. Melanocytes produce melanin, the pigment that gives skin its colour. The term “junctional” is used because the melanocytes in a junctional nevus are located at the junction between the epidermis and the dermis. This type of growth is commonly called a “mole,” a term used for any growth made up of melanocytes.

Junctional nevi (the plural of nevus) are typically found in individuals with lighter skin tones and can appear anywhere on the body. They are usually light in colour, but their appearance can vary depending on factors like skin type and the age of the nevus.

 

Normal skin histology

Is a junctional nevus a type of cancer?

No. A junctional nevus is a non-cancerous growth.

Can a junctional nevus turn into melanoma over time?

About one-third of all melanomas (a type of skin cancer made up of melanocytes) are believed to arise from previously non-cancerous melanocytic nevi. However, because junctional nevi are so common, the risk of a junctional nevus turning into melanoma over time is very low.

What causes a junctional nevus?

A junctional nevus is caused by prolonged exposure to UV light (typically the sun) and genetic susceptibility.

What is the difference between a congenital nevus and an acquired nevus?

A junctional nevus that develops shortly after birth is called a congenital nevus. A junctional nevus that develops later in life (as a child or an adult) is called an acquired nevus.

What are the symptoms of a junctional nevus?

Most junctional nevi are flat and round to oval in shape. The border between the nevus and the surrounding normal skin is usually well-defined and easy to see. Without a microscope, these tumours can look pink, brown, black, or blue, with most only showing a single colour.

How is this diagnosis made?

This diagnosis can only be made after a pathologist examines a tissue sample under the microscope. This usually involves removing the entire nevus in one piece, along with a small amount of surrounding normal-appearing skin.

Microscopic features

When examined under the microscope, junctional nevi comprises large round melanocytes. The melanocytes in a junctional nevus are found in a thin layer of tissue at the skin’s surface called the epidermis. The melanocytes are found within the epidermis in small groups called nests or spread out as single cells near the bottom of the epidermis. Over time, the melanocytes in a junctional nevus will spread down towards another layer of tissue called the dermis. When the melanocytes are found in the epidermis and the dermis, the growth is called a compound nevus. When the melanocytes are found only in the dermis, the growth is called a dermal (or intradermal) nevus.

nevus

Does a junctional nevus need to be removed?

In most cases, a junctional nevus does not need to be removed. These moles are usually harmless and do not cause any health problems.

However, removal may be recommended in certain situations, such as:

  • Changes in appearance: If the nevus changes in size, shape, or colour, or develops irregular borders, it should be evaluated by a doctor. These changes could be signs of atypical cells or, in rare cases, early melanoma.
  • Location: Nevi in areas prone to irritation, such as where clothing or jewellery rubs against the skin, may be removed to prevent discomfort or injury.
  • Cosmetic reasons: Some people choose to have a nevus removed for cosmetic purposes if it is in a visible location.
  • Uncertainty about the diagnosis: If the nevus looks unusual or is difficult to distinguish from other types of lesions, your doctor may recommend removal for further evaluation under a microscope.

If removal is recommended, it is usually done through a simple surgical procedure. Your doctor will explain why removal is being suggested and what to expect during and after the procedure. Regular skin checks and monitoring are important for all moles, including junctional nevi, to ensure they remain benign.

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