A mole should be examined by a dermatologist if it is larger than a pencil eraser or different in appearance than other moles, according to WebMD. Moles that first appear during adulthood, are asymmetrical, contain multiple colors or have irregular borders are of particular concern.
While most moles are noncancerous, irregular moles are linked to skin cancers such as melanoma. A dermatologist can take a sample of the tissue and send it for lab testing to determine if the mole is cancerous, reports the National Cancer Institute. It is estimated that 1 in 50 men and women are likely to be diagnosed with melanoma during their lifetimes, as stated by the Skin Cancer Foundation.