Moles, medically known as nevi, are common skin growths that develop from pigment-producing cells called melanocytes. These spots vary in size, shape, and color, appearing on almost everyone. While most moles are harmless, some exhibit unusual features that warrant closer attention. These are called atypical nevi, also known as dysplastic nevi. Understanding what constitutes an atypical nevus and when it might indicate a concern is important for skin health.
Understanding Atypical Nevi
An atypical nevus is a mole with unusual characteristics, distinguishing it from a common mole. The term “dysplastic nevus” refers to a mole with irregular features when examined under a microscope. While benign (not cancerous), these moles possess cellular and architectural features that differ from typical moles. Common moles show a uniform appearance, whereas atypical nevi can exhibit disordered growth patterns and melanocytes with varying sizes and shapes.
Microscopic examination of atypical nevi reveals features such as an increased number of melanocytes along the basal layer of the skin, irregular nests of cells, and architectural disorder. These cellular irregularities, referred to as atypia, can range from mild to severe. An atypical nevus is not a form of skin cancer, nor is it a precancerous lesion guaranteed to become cancer. Instead, it represents a distinct type of mole on a spectrum between common moles and melanoma.
Identifying Atypical Nevi
Identifying an atypical nevus involves observing specific visual characteristics remembered using the “ABCDE” rule. This mnemonic helps recognize features that may indicate a mole requires professional evaluation. Asymmetry means one half of the mole does not match the other in shape or appearance. Common moles are typically symmetrical.
An irregular border means the edges of the mole are uneven, notched, or blurred, rather than smooth and well-defined. Color variation within the mole is also a significant sign, including multiple shades of brown, black, tan, red, white, or blue within the same lesion. Atypical nevi are often larger than common moles, typically exceeding 5 or 6 millimeters (about the size of a pencil eraser). Evolution refers to any noticeable change in a mole’s size, shape, color, or symptoms like itching or bleeding over time. Any of these “ABCDE” signs warrant a consultation with a dermatologist.
The Significance of Atypical Nevi
Atypical nevi are significant due to their association with an increased risk of developing melanoma, the most serious form of skin cancer. While a single atypical nevus rarely transforms into melanoma, their presence indicates a higher predisposition for melanoma. People with multiple atypical nevi, especially ten or more, face a significantly elevated risk, potentially 12 times greater than individuals without such moles. This increased risk is not because the atypical nevus itself becomes cancerous, but because it serves as a marker for a person’s general susceptibility to melanoma.
Melanoma can develop within an existing mole, including an atypical nevus, but often arises on seemingly normal skin. Atypical nevi are considered risk indicators rather than direct precursors that invariably transform into cancer. Their presence signals increased vigilance for skin surveillance. Certain genetic factors, such as familial atypical multiple mole and melanoma (FAMMM) syndrome, can further amplify this risk, leading to a very high likelihood of developing melanoma.
Medical Evaluation and Care
Medical evaluation of suspected atypical nevi begins with a thorough visual inspection by a dermatologist. The doctor may use a dermatoscope, a handheld device that magnifies the mole and illuminates its underlying structures, helping distinguish atypical features from melanoma. For suspicious moles, a biopsy is often recommended for a definitive diagnosis. This procedure involves removing all or part of the mole for microscopic examination by a pathologist.
Management options for atypical nevi vary depending on biopsy results. Mildly atypical nevi may not require further treatment beyond regular monitoring. However, moles identified as moderately or severely atypical, or those with concerning changes, are often surgically removed with a small margin of surrounding healthy skin to ensure complete excision and rule out any underlying malignancy. Regular skin self-examinations and professional skin checks by a dermatologist, typically once or twice a year, are important for individuals with atypical nevi to detect new or changing moles early. Photographic documentation of moles can also assist in tracking changes over time.