Moles: What are They? When to Worry?

What are They?  When to Worry?

Everyone has them, increasingly people are worried about them.

So, what is a mole, why do we worry about them, when should we worry about them.

Some mole basics
The word mole comes a very old root from which other words meaning spot, or stain, or blemish arise.    And in common use today, the word refers to small, typically dark brown or black, spots or blemishes on the skin.

Nearly everyone has moles, and they are made up of the same type of cells, the melanocytes (muh-LAN-o-sites).

Melanocytes are cells with a unique function, they make a chemical called melanin, the key pigment of human skin.   The way it works is that each melanocyte has a network of little tubes, one tube going to from the melanocyte to a skin cell.  Typically each melanocyte is connected to about 50 skin cells.   As the melanocyte make their yellow pigment melanin, it is delivered through these 50 tiny tubes to 50 skin cells.

Nearly everyone has the same number of melanocytes, distributed in an even blanket across the skin, feeding nearly every skin cell with its melanin.   People with dark pigmentation have no more melanocytes than those of very little pigmentation.  The only difference is how much melanin is pumped out from one's melanocytes.  A very little bit or almost none will yield a person with very pale unpigmented skin.  More leads to olive or even slightly yellowish hues.  As melanin production increases, skin color tends towards the various shades of brown.

Almost everyone has a group of melanocytes accumulate somewhere on their skin, not the even sheet distributed across the skin described above, but a little ball of melanocytes.   This is a mole.

The average number is about 10-20.  It is thought the number of moles a person will develop, and where they will appear, is determined prior to birth in one's genes.

The number and place of moles is determined once one's genes are set, but these little balls of melanocytes, the moles tend to take many years to form. That's why most moles are not present at birth.  Many tend to develop during infancy and childhood and even appear during adulthood.
The little clumps or balls of melanocytes grow over time and so they may start flat and then grow to have some vertical elevation relative to the flat plane of the skin.

Moles tend to be some shade of brown.  They can be without any pigment, just flesh-colored, or very light brown,  Or, they can be darker brown, even to the point of looking black.  Some have a reddish hue as well.  Some have a little halo of decreased pigment or lighter skin surrounding them.

An enduring question about moles is, why do we have them?  No one has ever answered this question, so it remains in place.   My own sense is that they are present either because this a by-product of having a vast network of melanocytes across nearly all of our skin and sometimes they gather into clumps at random.  Or, they serve some function that we don't know about yet.

The main point about moles though, is that they are a normal part of the human body.  Nearly everyone has them, and unless they change in some radical way, they are 100%, completely harmless.

Why worry about moles?
If moles are a normal part of the body, why is there so much worry about them?

It should come as no surprise, but moles are like many other normal parts of our body, their cells can turn cancerous.   Not all parts of the body can create cancers, heart cells and nerve cells cannot turn cancerous.  But many other parts of the body can, like other parts of the skin, lungs, pancreas, kidneys, white blood cells, the gut cells.

Of course, cancer is a scary property of our bodies, one of the scariest, so it makes sense for us to be worried about whether our bodies, and especially our children's bodies, will every turn to cancer.

But moles have a special place in our world of worry.  We don't tend to worry much, when feeling fine, about our lungs, or gut.  In fact, if pushed to think about the insides of our body, most of us tend to be very grateful our lungs and gut, and other parts are doing their job.

But since moles have no known job to perform, they seem to sit there as a constant reminder of what might go wrong.  Moles, more than any other normal part of the body tend to make us think of cancer.   No wonder we worry more about our moles than any other part of our body.

What is melanoma?
Every cancer comes from a normal cell.  Most cancers are named for their cell of origin.  Lung cells are the cell of origin for lung cancer, and colon cells are the cell of origin of colon cancer.  But some cancers have their own name, usually tied to the cell of origin by some Latin or Greek translation.
White blood cells, for example, are the cell of origin of leukemia.  The ancient Greek word for white is leukos, and the ancient Greek word for blood is haima.  So leukemia is a rough Greek translation of the phrase white blood, referring to the white blood cell.
Melanoma comes from the Greek word for black (melos) and tumor or mass (oma), so it means black tumor.   But the cell of origin for melanoma is always a melanocyte.
Now, interestingly enough, most melanomas come from those melanocytes evenly distributed around the skin, not from moles.  In fact, about 75% of melanomas do not come from moles.  Of course that means about 25% of melanomas come from moles.
Melanoma is an unusual cancer since when it occurs, it makes itself visible via changes in the skin.
And so it has the very wonderful property that if the change is seen early enough, and it is removed before it goes even 1mm deep into the skin, it is cured.  No spread, no recurrence, cured.
Sadly, if it is missed, and goes very deep, it spreads better than most cancers and can be very deadly.

When is a mole worth our concern?
Of course, the only reason to worry about a mole is if its melanocytes convert to cancerous melanoma cells.  No melanoma no worries.  Thankfully, moles, like other parts of the body do not tend to convert, they stay normal our entire lives.   And, if a mole stays a mole, there is truly nothing to worry about.

So, the only reason to worry about a mole is if it is turning from a mole into a melanoma.   The key signs of that happening all have to do with change.  No mole starts off as a melanoma, so to become worrisome, a mole must change.

But it is is very important to keep in mind there is one change in a mole that is always fine, and always expected- they grow with you.   A mole on your belly at age 3 grows as the 3 year old grows, and maintains roughly the same proportion of area on the belly when you are 20 as when you were 3.

The changes of concern are easy to remember, as easy as A-B-C:
Area-  as noted, moles grow as a person grows, so they do increase in area normally, but if the mole grows beyond it usual proportion of area, that is of concern.   Moles smaller than the diameter of the eraser on a pencil are considered a normal, small size.
Border-  the border of a mole should not change.  Typically the border is very sharp, if the usually sharp border gets fuzzy or zig-zagged, that is of concern.
Color- moles come in all colors, but once a mole has appeared, its color should not change.  So if a mole gets darker, or develops more than one color, that is of concern.

The Gray Zone of Dysplasia
We have noted that moles either are simply moles, harmless clumps of melanocytes that don't do anything; or, are melanomas.

There is one other way moles can be, they can be dysplastic.  When we look at a mole under a microscope, we can see the melanocytes arranged in very orderly patterns, all looking exactly alike.  That's the normal mole.  Or we can see cells transformed into wild out-of-control clumps of growing chaotic looking cells.  That's melanoma.

Dysplasia is a state where the cells aren't as uniform, tidily arranged, and orderly as in a normal mole. But they aren't as wild and out-of-control, and oddly shaped as melanoma cells.   Dysplastic moles have melanocytes that are a bit disorganized, a bit non-uniform.  These are not cancers.   

Dyplasia means that the cells of the mole are a bit disorganized, but not that they are cancers.  It doesn't even mean they will become cancers.   If a mole turned dysplastic, but never turned to melanoma, it could stay on the body your whole life and never cause any harm.

The problem when it comes to the cancer melanoma is that any melanocyte can turn into melanoma, whether in the normal skin, in a normal mole, or a dysplastic moles.  Dysplastic moles turn into melanoma more often than normal moles, but the vast majority of dysplastic moles never do change, and most melanomas do not even come from moles.

The Current Craze to Remove and Biopsy
Now we come to current habits of how we all respond to the moles we all seem to have.

As noted above, we live in an era in which moles are far more scary than other parts of our body, even though so many parts of our bodies can turn into cancer.  It seems as though the fear of cancer, which is a very reasonable thing to dread, comes to the surface when it comes to moles.

Most would agree that any mole that poses a serious risk of being a melanoma needs to be removed and studied to see if it is.

The more interesting question is what about removing normal looking moles?  How to decide whether to worry about one, remove it and study it.

The answer turns out to be quite different for kids and older adults.   That is because the usual melanoma takes many, many years to transform its once normal melanocyte cells into melanoma cells.

To put this into some perspective, consider the how many people get diagnosed with melanoma a year.  For kids 0-14 years of age, that number is 1-3 out of every million kids.  For adults that number is 216 out of every million adults, about 200 times more common!!

This leads to perhaps the most interesting number I have come across when it comes to what happens to all the moles removed from kids.   This number is astounding, and was presented to me at a conference on pediatric dermatology not long ago.  The dermatologist stated that currently only 1 in every 100,000 moles removed in children turns out to be actual melanoma.  

That means that under current rates of mole removal, there are 100,000 moles removed that are perfectly harmless for every one that is.   There are no other procedures in medicine I know of where so many surgeries are done to that many people with no problem, for every one that is.

Which moles should be removed in childhood

There are a set of very unusual moles called large congenital nevus.  This is a very large mole, typically over 8 inches across, and present at birth.   These convert to melanoma at a higher rate than any other mole at any age, and need to be removed.

Otherwise, if a mole is present in childhood, is small, uniform in color, with sharp borders, has no spontaneous bleeding, the only reason to remove it is if it changes in those characteristics.  Removal for any other reason would be for appearance.

That means the typical mole should be removed for these reasons:
1.  Change in color
2.  Getting larger than expected with normal growth proportionate to the child's health
3.  Developing a fuzzy border,
4.  Changing in shape.

A good set of pictures contrasting typical, harmless moles, with worrisome moles is at

1.  Moles are a normal part of the normal human body, almost everyone has some, often as many as 100.
2.  Like other parts of the body, moles can become the cell source for cancers, in their case, melanoma.
3.  Even if everyone got all their moles removed, about 75% of melanomas would still occur, since most melanocytes are distributed across all our normal skin.
4.  The risk of melanoma developing from a melanocyte goes up with age, melanoma is quite rare in childhood.
5.  Well beyond the vast majority of moles removed in childhood turn out to be harmless, not cancerous.   If you took 100,000 moles removed from children, on average only one of them would turn out to be dangerous.
6.  A dysplastic mole in childhood is not a cancerous mole.   There is no direct way to know if a specific dysplastic mole will ever convert to a melanoma, just as there is no direct way to know if any spot of skin will at some time.
7.  Putting it all together, aside from the very rare instance of a large congential nevus (a mole >8inches across), the only clear medical reason to remove a mole from a child is if the area, symmetry, color, border, are worrisome as a result of it being too big, too asymmetric, changing, or bleeding.  Simple appearing moles that don't change or bleed or erode are very, very likely to be safe to leave alone.

To your health,
Dr. Arthur Lavin

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