Naevoid Melanoma

Naevoid melanoma is a rare and dangerous type of skin cancer that looks deceptively harmless, often resembling an ordinary mole. This similarity makes it one of the most difficult melanomas to identify, which can lead to delayed diagnosis and treatment.

Table of contents

• What Is Naevoid Melanoma?
• How Does It Look?
• How Is It Diagnosed?
• Who Gets Naevoid Melanoma?
• How Is It Treated?
• What Can Happen If Left Untreated?

What Is Naevoid Melanoma?

Naevoid melanoma is a malignant neoplastic lesion of the skin, meaning it is a cancerous growth. It is a specific type of melanoma, which is the most dangerous form of skin cancer^[1]. What makes naevoid melanoma particularly concerning is that it mimics the appearance of a harmless skin mole, called a nevus, both in how it looks to the eye and sometimes even under the microscope^[4].

This type of melanoma is considered rare. Estimates suggest that naevoid melanoma accounts for somewhere between less than 1% to as much as 3% of all melanoma cases^[1]. Like other melanomas, naevoid melanoma can become life-threatening through a process called metastasis, where tumor cells break away and spread to other parts of the body^[1].

How Does It Look?

Naevoid melanomas are extremely difficult to spot because they look so much like benign, or harmless, moles that many people have on their skin^[1]. The color is typically black or brown, though closer examination with special tools may reveal small patches of blue, gray, or other colors that are too subtle to see with the naked eye^[1].

These melanomas often appear as isolated bumps called papules, raised areas called nodules, or wart-like growths. One of the most misleading features is that they are often perfectly or nearly perfectly symmetrical, with smooth, rounded, and regular borders^[1]. These are exactly the characteristics that would suggest a harmless mole rather than a dangerous melanoma, which is why they are so easy to miss.

The way naevoid melanoma looks when first diagnosed can vary greatly. Some melanomas start out looking completely normal but then change appearance over time. They may become sore-like with bleeding, develop a shiny surface, or start looking more like a typical melanoma. Any normal-looking mole that rapidly changes its appearance should be considered suspicious and examined by a doctor^[1].

Most naevoid melanomas appear on the trunk (chest, back, or abdomen) and limbs, though they can develop anywhere on the body. The growths are often larger than 1 centimeter in diameter and can have a bumpy or dome-shaped appearance^[4].

How Is It Diagnosed?

Diagnosing naevoid melanoma requires careful examination using several techniques. Even with advanced tools, it can be challenging to distinguish from a harmless mole.

A tool called a dermatoscope can help doctors see details that are invisible to the naked eye, such as slight discoloration, irregular borders, and patterns that are more typical of melanoma^[1]. During a dermatoscopic evaluation, doctors look for specific warning signs including white lines, unusual blood vessels, gray dots or clumps, and multiple colors in the same lesion^[4].

However, some naevoid melanomas preserve normal layers of skin above them, making them difficult to identify even with a dermatoscope. For this reason, doctors often need to remove the suspicious lesion completely and examine it under a microscope^[1].

Under the microscope, pathologists look for several tell-tale signs that indicate malignancy rather than a benign mole. These include slight variations in cell shape called pleomorphism, abnormal-looking cell centers with prominent structures called nucleoli, and high rates of cell division known as mitotic activity^[1]. Other important clues include patterns where melanocytes (the pigment-producing cells) cluster together in unusual ways, form parallel arrays of nested cells, and lack normal connective tissue^[1].

The diagnosis can be particularly tricky because naevoid melanoma shares many features with benign moles. Subtle signs that help doctors differentiate include the presence of multiple cell divisions deep in the tissue layers, prominence of nucleoli, slight asymmetry, and unclear boundaries^[4].

Who Gets Naevoid Melanoma?

Naevoid melanoma shows some clear patterns in terms of who is most likely to develop it. The condition more commonly affects men than women. Age at diagnosis is typically in the sixth decade of life, with average ages ranging from 51 to 57 years^[4]. However, the disease can occur at any age, including rare cases in young children.

Because naevoid melanoma represents only a small percentage of all melanomas (between less than 1% and 3%), it remains a relatively uncommon diagnosis^[1]. Nevertheless, its ability to masquerade as a harmless mole means it may sometimes be under-recognized, leading to delayed treatment.

How Is It Treated?

Treatment for naevoid melanoma typically focuses on surgical removal of the primary tumor. The main goal is to completely remove the melanoma along with some surrounding healthy tissue to ensure all cancer cells are eliminated^[1].

Depending on the stage and extent of the disease, additional treatments may be necessary, just as with other types of melanoma. These can include chemotherapy, which uses drugs to kill cancer cells, radiotherapy, which uses high-energy radiation to destroy cancer cells, and other cancer treatments^[1].

One important medical consideration is that naevoid melanoma is never considered to be “in-situ” when treating a patient^[1]. This means that even if the cancer appears to be contained on the surface, doctors treat it as having the potential to spread.

What Can Happen If Left Untreated?

Naevoid melanomas progress at the same rate as other types of melanoma, meaning they can grow and spread over time. One particularly concerning aspect is that the primary tumor may appear small on the surface while already penetrating deeply into the tissue layers below^[1].

Once cancer cells reach blood vessels or lymphatic ducts (the tubes that carry fluid throughout the body), they can travel to other parts of the body. This creates what doctors call disseminated cancer, where the disease has spread beyond its original location. When melanoma spreads in this way, it ultimately can lead to death^[1].

The risk of delayed diagnosis is particularly serious with naevoid melanoma. Because it looks so much like a harmless mole, patients and even doctors may not recognize it as cancer right away. This delay in diagnosis and treatment can have devastating consequences, as the melanoma has more time to grow deeper and potentially spread^[4].