Moles

Overview

Melanocytic naevus, commonly known as a mole, is a very common benign skin lesion that results from the proliferation of melanocytes (pigmented cells). Moles can be present at birth, in which case they are referred to in medical dermatology as congenital naevi. Approximately one percent of the population is born with one or more moles. Moles that develop over the course of a person's lifetime are referred to as acquired naevi.

In medical dermatology, moles have a distinct dermatoscopic and histological appearance. They can be flat or protruding and may appear on any part of the body. The location on the body influences the overall appearance of the lesion. Moles vary in colour, ranging from pink to black, and in size, ranging from a few millimetres to a few centimetres in diameter. They typically present with a rounded shape, though irregular shapes are occasionally observed.

Causes and Risk Factors

The exact reason why moles appear is not yet fully understood. The number of moles present on the body is influenced by several factors, including genetic predisposition, immune status, and prolonged sun exposure.

Individuals with lighter skin tones are predisposed to having more moles than those with darker skin. A familial pattern is commonly observed, with higher mole counts tending to occur across family members. Additionally, individuals who undergo immunosuppressive treatment may experience an increase in mole numbers as a side effect of that treatment.

Individuals with lighter skin typically have light-coloured moles, while those with darker skin more commonly present with dark brown or black moles.

Signs and Symptoms

Most melanocytic naevi are benign and do not cause symptoms. However, certain features warrant closer evaluation. Despite their generally benign nature, melanocytic naevi can be mimicked by melanoma, one of the most serious forms of skin cancer. In its early stages, melanoma may resemble a regular mole, but it tends to enlarge over time and develop a more irregular shape.

Features that may indicate a mole requires further assessment include:

• Asymmetry: one half of the mole does not match the other.
• Border irregularity: the edges are uneven, notched, or poorly defined.
• Colour variation: multiple shades of colour are present within a single lesion.
• Diameter: the lesion is greater than six millimetres in diameter.

Moles that are itchy, cause bleeding, or appear crusty are also indications for a more detailed clinical assessment. Individuals who develop new moles after the age of 40 are considered to be at elevated risk of melanoma.

Diagnosis

In clinical practice, moles are assessed through dermatoscopy, a technique that uses skin surface microscopy to examine the structure and patterns of the skin. Key features evaluated during dermatoscopic examination include changes in size, colour, shape, and internal structure.

When a naevus appears suspicious for melanoma, a diagnostic biopsy is performed. This may involve excision biopsy (complete removal of the lesion) or incisional or punch biopsy (removal of a representative portion of the tissue) for subsequent histopathological laboratory analysis.

Treatment Options

Melanocytic naevi are typically removed only in cases of suspected malignancy or for cosmetic purposes. Surgical removal techniques include excision biopsy for flat moles and shave biopsy for protruding moles. Removal by radiofrequency surgery is also available. When removal is indicated, the most appropriate technique for achieving minimal scarring is discussed with the patient by the dermatologist.

When to Seek Medical Attention

A dermatologist should be consulted if a mole changes in size, colour, shape, or structure; if it bleeds, itches, or becomes crusty; or if a new mole appears after the age of 40. Individuals with a large number of moles are at higher risk of developing melanoma and are advised to have their naevi monitored regularly by a qualified dermatologist. At the Centre for Medical and Surgical Dermatology, Dr. Maksym Breslavets provides individualised assessment and management of melanocytic naevi.