A mole (nevus) is a common skin growth that develops when pigment-producing cells, called melanocytes, cluster together. Most people develop between 10 and 40 moles, and the vast majority are benign. While changes in a mole’s appearance are a normal part of its life cycle, the speed of these changes determines if medical attention is needed. Rapid growth or alteration is the primary concern, as it can signal melanoma, an aggressive form of skin cancer. Understanding the difference between slow, decades-long change and quick, concerning change is important for skin health.
The Timeline of Normal Mole Development
Moles typically appear during childhood and adolescence, with new moles developing until the early 30s. These acquired moles usually start as small, flat spots and may later become slightly raised, a transformation that takes many years. This slow, gradual change indicates a mole is maturing and is not usually a cause for worry.
Normal growth is measured in years, not weeks or months. Over decades, a mole may darken, fade, or become softer as the melanocytes are replaced with fibrous or fatty tissue. A typical benign mole is generally small, usually less than 6 millimeters.
Moles present at birth, known as congenital nevi, also grow slowly as a child grows. Individuals with 50 or more moles, or those with atypical-looking moles, have an increased risk of developing melanoma. While slow evolution is generally benign, any new mole that appears after age 40 should be checked by a professional.
Factors Influencing Mole Growth and Appearance
The appearance of new moles and the alteration of existing ones are driven by internal and external factors. Genetics determine an individual’s predisposition to having a high number of moles and influence how skin cells respond to environmental triggers. Gene variants can affect the proliferation and color of melanocytes, leading to a higher risk for mole formation.
Ultraviolet (UV) radiation exposure is the primary external trigger that causes changes in moles. Sun exposure stimulates melanocytes to produce more melanin, which can cause existing moles to darken or new moles to form. Moles may appear more prominent or numerous following periods of intense sun exposure.
Hormonal fluctuations also stimulate melanocyte activity, making moles more noticeable. During significant hormonal shifts, such as puberty or pregnancy, existing moles may become temporarily darker or larger. The surge in hormones like estrogen and progesterone triggers increased melanin production, a change that is typically temporary.
Identifying Rapid and Concerning Mole Changes
When a mole changes over a period of weeks or a few months, this is considered rapid growth and warrants immediate evaluation. Unlike the decades-long maturation of a benign mole, a sudden, noticeable change in size, shape, or color can indicate that the melanocytes are growing uncontrollably, which is the definition of melanoma.
The ABCDE criteria provide a structured way to track changes and identify potentially dangerous moles:
- Asymmetry: One half of the mole does not match the other.
- Border irregularity: Edges are uneven, notched, or blurred.
- Color variation: The mole has multiple shades, such as different tones of brown, black, red, or blue.
- Diameter: Refers to a mole larger than 6 millimeters, though melanomas can be smaller when first detected.
- Evolving: Focuses on any rapid change in size, shape, elevation, or color.
New symptoms such as persistent itching, bleeding, crusting, or the development of a non-healing sore within the mole are also significant signs of evolution that require prompt medical attention. If a mole meets any of these criteria or simply looks different from all the other moles on your body, it should be examined by a dermatologist.