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Pigmentation is the skin is produced by specialised cells in the skin called melanocytes. These are present in everybody in equal numbers, including people of dark or lighter skin colours. This might come as a surprise as one would expect more melanocytes in someone of darker skin colour. However the only difference in someone with darker skin is that the melanocytes in people of darker skin types are hyperactive, enlarged and produce more pigmentation, compared to the melanocytes in white skinned races.

The word ‘mole’ is commonly meant to imply an area of the skin (usually a few mm in diameter)  which is darker than the surrounding skin. In medical terms moles are referred to as ‘naevi’ (naevus= singular). These lesions are usually caused by an excess number of melanocytes (pigment producing cells) in the area (as opposed to a freckle, which is caused by a normal amount of pigment producing cells which being activated by sunlight, produce excessive pigment i.e. the number of melanocytes in the area is within normal limits, unlike moles).

Most moles are flat and one cannot feel them raised. However it is also quite common to have moles that are raised (because the melanocytes are significantly more in number and form a lump under the skin) or even have hairs growing through them. This is not a worrying sign by itself. In these instances it is also normal for the mole to be of normal skin colour and not be dark. This is because the lesion just has an excessive number of melanocytes but these cells are not mature enough to produce any pigment. Again, this is entirely normal. So basically moles can vary in colour from being skin coloured to dark black.

Most people are born with one or two moles (which we call birthmarks). But, it is not uncommon for these lesions to only become apparent as one grows older. These types of moles that appear at or just after birth are called congenital naevi. Most of the moles we see in adults however are acquired in later life, usually due to sun exposure (acquired naevi). In fact one can develop new moles in adult life until the age of 60, and this is completely normal. Most often the mole appears and grows in size gradually for a few months, before stabilizing. It is interesting that after the age of 60, one actually starts to gradually lose the moles acquired during adult life. This is again normal.

So when should one worry about moles?

The ABCDE rule for moles is well know anyway. For those who don’t:

  • A= Asymmetry- if you draw a line through the middle of the mole, the two halves are not approximate mirror images
  • B= irregular Border- if the mole has Ill-defined or blurred  borders
  • C= varying Colours- if the mole has different colours within
  • D= Diameter more than 5mm
  • E= irregular Elevation- if the mole has flat and bumpy components

Apart from ABCDE, one should worry about moles if

  • There is a family history of melanoma
  • If one has more than 100 moles on the body
  • One has used sunbeds extensively or has been an ardent sun worshipper (especially if you have had a lot of sunburns causing blistering)
  • A mole appears and keeps growing in size, without showing any sign of stabilising (there is no definite time limit but I usually suggest an arbitrary limit of 2 months for moles to keep growing)
  • A mole is either itching or bleeding

Online resources available if you are still worried:

Obviously if you you have a worrying mole, it would be best to see a dermatologist in person. A dermatologist would be able to look at the lesion under a special magnifying lens called a dermoscope, and be able to decide whether it can be left alone, needs to be monitored, or cut out.