Atypical Melanocytes

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Atypical melanocytic lesions are also known as dysplastic nevus or dysplastic mole, atypical mole, or atypical melanocytic hyperplasia. Mole and nevus are synonymous. By definition these lesions are benign. However, since this terminology is based on either a visual inspection or a partial biopsy of the lesion, the real diagnosis may be something more serious. Complete lesion excision and examination under a microscope is needed.

Signs of Atypical Melanocytic Lesions

Atypical Melanocytic lesions are irregular moles and skin spots that require further examination. The five visual characteristics used to identify an atypical melanocytic lesion are the same as the characteristics used to identify signs of invasive melanoma. These are called the ABCDE’s of melanoma.


  1. Asymmetry, one side of the mole is different from the other
  2. Borders that are irregular, blurred, or not even
  3. Color that is abnormally dark,different, or variable within a single lesion
  4. Diameter greater than 6 mm, a pencil eraser.
  5. Evolution of a mole's appearance, i.e. changes in color, size, or shape.


These signs require a biopsy of the lesion to rule out melanoma.

Diagnosis And Treatment

Atypical melanocytic lesions are pigmented moles that have abnormal cells under a microscope. These lesions will need to be evaluated by excision (removal) and evaluation by a dermatopathologist in a laboratory setting. If the evaluation results show that the entire lesion has not been removed, the remaining part of the lesion will need to be taken for further evaluation. If evaluation proves that the lesion is benign, no further treatment is required.  There is some controversy regarding the excision of additional margins around a previous biopsy. Rationale for additional excision is to prevent the risk of melanoma developing in a few remaining abnormal cells. This is largely unproven but is frequently performed in the US.


Pathologists classify atypical melanocytic lesions as mild, moderate, or severe. Excision of additional margins should only be performed on the severely atypical lesions, if at all. In any of these classifications, complete lesion excision is necessary for the dermatopathologist to make a proper diagnosis. This is because within a single atypical pigmented lesion, significant variation of microscopic findings can be present. For example, a melanoma may be misdiagnosed as an atypical lesion if only a small periphery of it is biopsied.


Patients with multiple atypical melanocytic lesions proven on biopsies are at higher risk of developing melanoma in their lifetime. These patients require regular skin checks and frequent biopsies.

Prevention and Detection



Atypical Melanocytic lesions are largely influenced by genetics. Still, SCARS Center skin cancer specialists promote skin cancer awareness and sun safety as your best form of protection against skin cancer. You can learn more about skin cancer within the content of this website, by following news about skin cancer, and by talking to a SCARS Center specialist. To practice sun safety, avoid peak hours in the direct sun (10:00 am - 4:00 pm), apply sunblock every two hours, and cover up whenever you plan to be in the sun. 





Detection of Atypical Melanocytic lesions can occur in the home, in a physicians office, and even in places such as the nail salon and hair salon. When checking for skin cancer, be sure to look under the feet and at the palms of your hands, have a loved one check your scalp, and remember to look in between fingers and toes. SCARS Center physicians recommend one at home skin check per family member per month, this includes small children and elderly family members, and an annual or  biannual (twice a year) skin check with your primary care physician or dermatologist. If at any point you notice something irregular or concerning, schedule an appointment with your dermatologist for evaluation.


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Learn more about detecting signs of melanoma skin cancer

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