Skin Moles

Typical acquired skin moles develop after birth, slowly enlarge symmetrically, stabilize, and persist or regress later in life. The majority of Typical acquired skin moles appear to develop during the second and third decades of life, although some lesions may appear in the first 6 to 12 months of life.
A number of studies have measured the number of typical acquired skin moles in different age groups. The average number of skin moles per person peaked at 43 for males and 27 for females during the second and third decades, respectively, and decreased to very few in the sixth and seventh decades. A similar age-related prevalence rate for skin moles has also been documented. A difference in frequency distribution of skin moles according to gender is not clear, although most series show a close to equal prevalence in males and females. The prevalence of skin moles varies according to race. In blacks, the overall prevalence of skin moles (regardless of size) tends to be higher in those with lighter skin versus those with darker skin. When prepubertal whites were examined for skin moles, a significant association for excess skin moles was documented for pale skin, blue or green eyes, blond or light-brown hair, and a tendency to sunburn, but not a tendency to freckle. Other studies show variable relationships to these same parameters. Environmental exposure to UV light appears to be a critical exacerbating factor for the development of skin moles. Mole density has been shown to increase with increasing sun intensity of UV light. Further, the use of UV blocking sunscreens has been shown to decrease the number of new moles in children. Genetics plays a role in mole development. There is evidence that the size, frequency, and distribution patterns of acquired skin moles tend to aggregate in families. This observation is well documented for atypical skin moles in the setting of familial cutaneous melanoma and congenital skin moles.