Can melanoma come from small, tiny moles?

Do you believe a mole can never turn into melanoma as long as it’s small or tiny?

If, during your monthly skin exams for cancer, you’ve decided to skip past your small, tiny little “birth marks” – you’re making a big mistake. I consulted with Neal Schultz, MD, a dermatologist with a private practice in the NYC area, and founder of dermTV.com.

Historically, the rules for self-screening for melanoma have been to pay attention to the ABCDs of mole inspection, in which the “D” stands for diameter.

And typically, the diameter to be suspicious of is anything larger than 4 millimeters, or “the size of a pencil eraser.”

That got me thinking, because what’s so magical about 4 or 5 millimeters such that any mole smaller would be resistant to turning into melanoma?

Dr. Schultz has this to say:

“When I was training in dermatology in the mid-1970s, the ‘rule’ was that if a mole was less than 4 mm in diameter (one-sixth of an inch), then it couldn’t be a melanoma already.

“We now know that moles as tiny as 1 mm (1/25th of an inch) can already be a melanoma.”

I saw two red melanomas on a 27-year-old man’s forearm that were about 1 millimeter or so.

However, they had not sprung from pre-existing spots or “birth marks.”

Can a pre-existing, normal mole, that is small … say, around 1 millimeter … ever transform into melanoma?

Dr. Schultz continues, “People often wonder whether melanoma arises from normal pre-existing moles, or whether they arise ‘de-novo,’ meaning just from a single melanocyte (pigment cell) in the skin, which then becomes cancerous and goes crazy.”

Between 2003 and 2007, 150 melanomas that Dr. Schultz had diagnosed were analyzed in the laboratory for a retrospective study.

It turned out that 23 percent of the cancers were shown to have originated within a precancerous spot – and this included 1 millimeter moles.

“But then you have to understand that when a melanoma is really advanced and far developed, even if it develops in an abnormal mole, it may have destroyed the original mole.

“So the 23 percent number is a minimum, but not a maximum, since some of the melanomas that I diagnosed may in fact have arisen in moles, which the melanoma completely destroyed, and therefore there is no way on knowing that in fact, it started in a mole.”

Pay close attention to your small birth marks, brown spots, freckles, sun spots, what-have-you.

Just because a pigmented lesion is very small doesn’t mean that the DNA in it is resistant to the mutational changes that lead to melanoma.

If a tiny little “birth mark” seems to be getting bigger or darker, have a dermatologist look at it.

Interestingly, whether or not small moles can ever turn into melanoma has not received any fine-tuned verdict by the medical community.

Dr. Schultz says that some physicians believe “melanomas never arise in preexisting benign moles, and other physicians such as myself believing that as many as 20-25 percent of melanomas arise in preexisting benign moles, which in my view is substantiated by studies such as the one I mentioned.”

Many patients have reported that they’d been aware of a mole for years, appearing stable, and then one day they noticed that the spot was changing – with the diagnosis ultimately being melanoma.

Melanoma under magnification. Shutterstock/Nasekomoe

So we know that melanoma, in the minority of cases, comes from pre-existing pigmented spots.

Many of these pre-existing lesions, in these cases, have always appeared normal, and were unchanging for years, present since childhood or birth.

Then the patient one day realizes that the spot’s been looking darker, or seems just a little larger.

  • The big question, then, is what percentage of melanomas-from-pre-existing-moles comes from spots that were only 2 millimeters small originally?
  • Only 1 millimeter?
  • Only just a tiny speck?

This data has not been established. Nevertheless, by all means, during your monthly skin exams for anything suspicious or questionable, do not dismiss any tiny moles that you know have “always been there.”

This is especially true if you’re not sure that the little speck has always been there in the first place, which is why it’s a very smart idea to create a map of all your skin’s lesions, so you can use it as a reference point every time you examine your skin for signs of melanoma.

Dr. Schultz has been treating his patients’ dermatologic conditions for 30+ years, with particular emphasis in skin cancer prevention and treatment, acne treatment and laser surgery.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  

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Top image: Shutterstock/ Albina Glisic