Atypical melanocytic lesions are also known as atypical melanocytic hyperplasia, atypical mole, or dysplastic mole. The majority of these are benign, however, some have a significant risk of developing into melanoma or actually being a melanoma. This terminology is applied based on either a visual inspection or a biopsy of the lesion.
Visual examination of skin can often identify suspicious lesions requiring further evaluation. Five visual characteristics are used to identify the risk of invasive melanoma:
A - asymmetry, one side of the mole is different from the other
B - borders that are irregular, blurred, or not even
C - color that is abnormally dark,different, or variable within a single lesion
D - diameter greater than 6 mm
E - 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 invasive melanoma.
Atypical melanocytic lesions are pigmented moles that have been found to have abnormal cells and are assumed to be at risk for developing into a malignant melanoma. These lesions, once diagnosed as atypical, are typically excised to eliminate the risk of cancer. Although this seems like a prudent approach, scientific evidence for this is frequently lacking. Rationale for excision is based on one extreme variant of the atypical melanocytic lesion - melanoma-in-situ or lentigo maligna. This is not an invasive melanoma.
There are four levels of classification of atypical melanocytic lesions:
Only melanoma-in-situ has adequate evidence to support surgical excision. This particular lesion carries a 5% risk of degenerating into malignant melanoma over a 50 year lifetime. This breaks down to a risk of 1% per decade. What no one knows is the risk of the other 3 lower grades of atypia. Logic would dictate that the risk would be even lower - if present at all.
What makes this more complicated is that the complete diagnosis of a melanocytic lesion requires a complete excision. These lesions frequently exhibit heterogeneity - variability of abnormality. In other words a lesion with moderate atypia may contain areas of melanoma-in-situ within it. Melanoma-in-situ lesion may contain areas of invasive malignant melanoma. Frequently, this variability is visible with a naked eye and guides the clinical decision making.
The controversy arises when destructive biopsy is undertaken in a cosmetically sensitive area such as face of a lesion diagnosed with mild to severe atypia. Although most surgeons will not hesitate to excise these lesions completely, scientific evidence to support such approach is lacking. To make matters worse, complete excision of these atypical lesions requires 2 - 5 mm margins for complete clearance.
Important questions remain: