From the Guidelines
A nevus can suddenly appear, but it is more likely that it was developing gradually and only became noticeable once it reached a certain size or pigmentation. Nevi typically develop during childhood and adolescence, though new moles can form throughout adulthood due to a combination of genetic factors and environmental exposures, such as sun exposure which stimulates melanocytes to multiply 1. Hormonal changes during puberty, pregnancy, or from certain medications can also trigger new nevus formation. While some nevi may spontaneously regress, as noted in a 2021 study published in Pediatrics 1, others may evolve over time, including changes in pigmentation, texture, and surface characteristics. It is essential to monitor any new moles using the ABCDE rule (Asymmetry, Border irregularity, Color variation, Diameter larger than 6mm, and Evolution or change over time). If a new mole exhibits concerning features or rapid changes, consultation with a dermatologist is crucial for evaluation, as this could potentially indicate melanoma or another skin condition requiring medical attention. Key factors to consider when evaluating a new nevus include:
- The patient's background skin pigmentation, which may influence the ultimate nevus color 1
- Changes in the texture or surface of the nevus, such as becoming more raised, hypertrichotic, or verrucous 1
- The presence of other risk factors, such as a family history of melanoma or excessive sun exposure.
From the Research
Nevus Appearance
- A nevus, also known as a mole, can suddenly appear, as seen in the case of Spitz nevus, which can develop rapidly and grow to a 1-cm diameter in 6 months or less 2.
- The sudden appearance of a nevus is not unique to Spitz nevus, as other types of nevi can also appear suddenly, although the exact timing and growth rate may vary.
Types of Nevi
- There are various types of nevi, including Spitz nevus, blue nevus, junction nevus, and compound nevus, each with distinct characteristics and growth patterns 2, 3, 4.
- The differentiation of these nevi is crucial, as some may be benign while others may be malignant or have the potential to become malignant.
Factors Influencing Nevus Development
- Sunscreen use has been shown to reduce the development of new nevi, particularly on intermittently sun-exposed body sites, suggesting that UV radiation may play a role in nevus formation 5.
- The development of nevi can also be influenced by genetic factors, as seen in the case of congenital nevi, which can appear at birth or shortly after 6.