Types and causes of moles- Biology Bug

What are moles?

Moles are the growth on the skin which are brown, black or red colored lesions which can appear alone or exist in groups. They can appear anywhere on your body including the eyes, nose, hands, legs, chest, back or even the genitals. The medical term for the moles is melanocytic nevus (visible chronic lesions on skin). Some people describe them as imperfection on the body while most of the beauty experts consider them as beauty mark. Most of the times moles appear in early childhood and during first 25 years. But have you ever thought what the factors which cause mole are? Let’s discuss some of them.

What causes mole?

  • Exposure to sun
  • Genetic factors
  • Hormonal imbalance

Exposure to sun

Every individual gets a distinct skin color because of different melanin levels. Melanin is a pigment which is produced by specialized skin cells called as melanocytes. These melanocytes produces more melanin when exposed to sun in order to protect the skin from harmful radiation. This is one of the reason why we get tan when exposed to the sun. Moles are concentrated clumps of melanocytes, which is why they look darker. A normal individual can have 15-30 moles. However the people with more number of moles have higher risk of melanoma. Melanoma is a type of cancer that develops from melanocytes. But most of the moles are non-carcinogenic in nature.

Role of genetics

The role of genetics is not well understood for mole development. However the study for melanoma has been widely published and hence we can relate it to development of benign moles. DNA present in the skin cells contains several genes. There can be mutation, hereditary factors or exposure to harmful radiation can result into variation of certain genes which includes FGFR3, PIK3CA, HRAS, and BRAF. Variation in these genes can lead to benign moles. For example, mutation in BRAF gene leads to production of an altered protein that causes melanocytes to aggregate into moles. 

Hormonal imbalance

Hormones can be imbalanced because of several reasons including pregnancy, menopause, puberty or medications. During pregnancy the level of progesterone and estrogen vary each month. Also there is small variation in amount of MSH i.e. melanocyte stimulating hormone which is produced by pituitary gland. MSH hormones stimulate the melanin production in melanocytes. Hence you can see dark or tan patches on the skin in case of pregnant ladies. It frequently occurs during the menopause since the hormonal level is fluctuating continuously and results into increase in either the size of mole or number of moles.

Types of moles

There are basically three types of moles that are symmetrical, irregular and regular. But in medicine it is divided into several types according to their location, shape and time of appearance.

Common moles

It is about 5mm large with distincy edges and dome like surface with brown pigmentation. They are found on the skin when exposed to the sun.


This type of mole shows irregular symptoms. They have blurry borders and can vary in color. They are comparatively larger than the common moles. Also they can be flat or raised lesions. If a person is having too many atypical moles then the risk of skin cannot be neglected. The person should go for regular examination.

Congenital moles

They are also known as congenital nevi. They appear at the time of birth or within first year of baby’s life. These moles can be caused by melanocyte cells in middle layer of skin, outer layer of skin or both. They can be referred as birthmarks.

Acquired moles

Acquired moles are moles that appear during childhood and adulthood. Most of these moles are benign and pose no risk, although sometimes they can turn into cancerous moles with age. This type of mole is the most common, and repeated sun exposure usually causes it. These moles appear during early childhood or sometimes in adulthood. This type of mole generally do not pose any risk in future. They are one of the commonly seen moles.

Junctional melanocytic moles

They occur due to accumulation of melanocytes where the dermis and epidermis meet. They are slightly raised with regular borders and dark pigmentation (range from tan to dark brown). As the age increases these moles can migrate down to deeper layers of skin.

Intradermal moles

They are skin colored moles and their pigmentation is not as dark as junctional ones because they are located in the middle layer of your skin. They usually develop during late childhood or throughout the adulthood.

 Now remembering all the types of moles with their unique qualities can be little difficult. Hence doctors have introduced ABCDE method.

A: Asymmetrical

B: Irregular border

C: Multiple color

D: Bigger diameter

E:  Evolving, new or changing

External Links:

  • https://www.webmd.com/skin-problems-and-treatments/guide/moles-freckles-skin-tags
  • https://www.healthline.com/health/new-mole#types
  • https://www.medicinenet.com/moles/article.htm#what_are_moles
  • https://ghr.nlm.nih.gov/primer/traits/moles
  • https://www.skinvision.com/articles/types-of-skin-moles-and-how-to-know-if-they-re-safe

Thanks for reading. Tell me which type of mole you’ve seen? Comment down below.