From the Guidelines
Asymmetry in a nevus (mole) is a concerning feature that warrants medical evaluation as it may indicate melanoma, and individuals should schedule an appointment with a dermatologist promptly for assessment if they notice asymmetry in a mole. Asymmetry is the "A" in the ABCDE rule for melanoma detection (Asymmetry, Border irregularity, Color variation, Diameter >6mm, and Evolution or change over time) 1. While many benign moles are symmetrical with even shapes, melanomas often grow irregularly, creating asymmetrical appearances. Not all asymmetrical nevi are cancerous, but this feature increases suspicion and requires professional evaluation. The dermatologist will likely examine the nevus with a dermatoscope and may recommend removal for histopathological examination if concerning features are present. Some key points to consider in the evaluation of a nevus include:
- The "ugly duckling" concept, which suggests that melanomas often do not fit the individual's nevus pattern 1
- The use of dermoscopy by an experienced physician to enhance diagnostic accuracy 1
- The importance of regular self-examination of the skin (monthly) and annual skin checks by a healthcare provider for early detection of problematic nevi, especially in individuals with risk factors such as fair skin, history of sunburns, or family history of skin cancer. It is also worth noting that melanoma may occur in the skin or the CNS, and some individuals with large or giant CMN have had metastatic melanoma without a known primary site 1. Therefore, any concerning changes, such as rapid growth, bleeding, pain, development of a lump or nodule, or ulceration, should be promptly evaluated by a dermatologist.
From the Research
Significance of Asymmetry in a Nevus (Mole)
- Asymmetry in a nevus can be an indicator of potential malignancy, and its assessment is crucial in distinguishing between benign and worrisome melanocytic lesions 2, 3, 4
- Dermoscopic features of common nevi, such as symmetry, regularity in shape, and uniformity of dermoscopic structures, can aid in the evaluation of pigmented lesions 3
- However, some types of nevi, like Spark's nevus, can exhibit dermoscopic asymmetry (63%) despite being benign 4
- Asymmetry was the most frequent indicator of histopathologic atypical Spitz nevus (79%) in one study, highlighting the importance of assessing asymmetry using both dermoscopic and histopathologic analysis 2
- The presence of asymmetry, along with other dermoscopic features like irregular pigmentation, atypical pigment network, and irregular globules, can make it challenging to differentiate between benign and malignant lesions 2, 4