Atypical Melanocytes

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.