Moles and Heredity

There are a number of genetic and epigenetic factors that affect the number and type of moles a person forms. The strongest determining influence in mole formation is heredity. A person who has a parent, or perhaps two parents, with a tendency to form moles is likely to have a similar tendency. Most people have some moles, although there are certain factors which make a person more likely to have a tendency to form multiple moles.

Most moles are classified as benign neoplasms, which means that they are benign tumors. Most people have between ten and forty moles that appear by the time they reach twenty years of age. Normal hormonal changes that teenagers and young adults experience may cause these moles to darken. Pregnancy hormones also cause existing moles to darken and may lead to new moles forming. Often as a person ages, moles will fade away or fall off. Twin studies involving both identical and fraternal (non-identical) twins demonstrated that individuals within a pair of identical twins had similar numbers and types of moles develop. The similarity was much less pronounced in pairs of fraternal twins. This similarity in identical twins demonstrates the significance of genetic factors regarding mole formation. While epigenetic factors such as exposure to sunlight are also significant in mole formation, the hereditary aspect of mole formation seems to be the primary influence.

Moles are infrequently present at birth; when a baby is born with moles, it can be a cause for concern, since congenital moles, moles present at birth, have a higher risk of becoming cancerous. Some parents choose to have these moles removed as soon as possible to minimize the risk of the mole becoming cancerous and to analyze the mole's tissue to assess future cancer risk. Larger congenital moles have a higher risk of becoming cancerous. This is because of genetic factors and because these moles tend to be on the face or neck. The areas where congenital moles are most frequently present are also areas that receive the most exposure to sunlight.

Since some moles are already at risk of developing into malignant tumors, exposing them to sunlight can aggravate a mole already predisposed to cancer. Larger moles in particular are likely to become cancerous. Giant moles, or moles that are large enough to cover a significant portion of the head or body, are a particularly high risk. Babies born with giant moles may have as high as a fifty percent chance of developing melanoma from a giant mole.

Moles and Skin Cancer

Since moles are technically benign tumors, some of the hereditary factors that influence mole formation are also factors that influence a person's predisposition to developing skin cancer. People who have fair complexions are more likely than people with darker complexions to form moles. Those with fair complexions are also more likely to burn under sunlight. Frequent, prolonged sun exposure is correlated both with mole formation and with skin cancer. Light hair and eye color are also connected to mole formation and skin cancer. This is likely because people with light skin, hair and eyes have less melanin in their bodies. Melanin, the pigment that gives moles their dark color and that gives skin its color, is a protein that gives the skin some protection from ultraviolet radiation. People with less melanin in their bodies are therefore more easily burned because their skin is unable to protect itself as well as it could if more melanin were present. The hereditary factors that contribute to light-colored skin, hair and eyes is therefore a contributing factor to mole formation.

Moles and Hormone Function

Hormonal factors also influence mole formation. Variation in hormone function is normal in human populations; such variations are often the result of heredity and epigenetic factors. Women tend to develop acquired moles, moles that appear after twenty years of age, more frequently than men do, though not all women form acquired moles. The difference in the frequency of acquired moles between men and women probably owes to the differences in hormonal changes experienced by men and women: women have more frequent periods of hormonal changes than men do. However, women experience periods of hormonal changes differently, including in whether new moles form and the number and type of moles that do form, indicating differences in hormone function that are likely hereditary. Thyroid imbalance, another condition that is often inherited, also contributes to mole formation, since the thyroid produces some of the hormones that influence mole development.

Atypical Mole Syndrome

Atypical mole syndromeAtypical mole syndrome is a condition which tends to run in families. Atypical moles are moles that deviate from normal moles in appearance, texture, color and other characteristics. Normal moles tend to be one color, have smooth texture and rounded, even edges. Atypical moles tend to be larger than benign moles and have irregular, ragged edges. Some may have several different colors and be elevated from the skin. These moles are most likely to develop into melanomas.

People with atypical mole syndrome have high numbers of benign moles and atypical moles. While normal numbers of moles range between ten and forty, people with atypical mole syndrome have over one hundred moles; some of these moles exhibit abnormal characteristics. Some families with a history of atypical mole syndrome also tend to inherit multiple melanomas. People with atypical mole syndrome who have a family history of melanoma have a lifetime risk that approaches one hundred percent of developing melanoma by the time they reach seventy years of age.

Mole formation is influenced by different genetic and epigenetic factors. Since heredity seems to be the primary factor in determining the number and type of moles a person will develop, people can look to their family history to assess their risk of their moles developing into melanomas. While family history of melanoma does not necessarily mean that a person will develop melanoma, knowing one's risks of developing melanoma can motivate a person to monitor their moles for changes and to take proactive steps to minimize their risk of mole-related cancer.