image from here
Why do moles grow hair?
A few days ago, I was on the train home when I noticed this uncle standing a few metres away from me. On one of his forearms was a large, okay gigantic, black mole, which had sprouted a bunch of thick black hair. (HAHA don’t even ask me why I notice such things! :X)
Anyway that got me wondering. Why do moles grow hair? Googled a bit and found this discussion thread, in which someone quoted a defunct site as saying:
Q What is the significance of hairs in a mole, and does their removal by plucking or electrolysis lead to melanoma?
Moles not infrequently are “hairy,” particularly those present since birth. Many lay people construe this as a sign of progression to cancer when in fact it emphasizes the benignity of the mole. As we age, previously fine, non-pigmented “vellus” hairs becomes thicker and pigmented, known as “terminal” hairs, for unknown reasons. This is common on the ears of men, and upper lip and chin of women. A similar process can occur within moles, that is, formerly inconspicuous vellus hairs become more noticeable. The enlarged or prominent hair follicle may also lead to a “pimple” or cyst. As a consequence a previously stable mole can rapidly enlarge in size or become inflamed, alarming the patient to think that his or her mole has become cancerous. Invariably the mole reverts back to its former state as the pimple or cyst recedes. The removal of hairs within moles by either plucking or electrolysis can similarly result in a pimple, but there is no proof that, or any form of trauma will result in the malignant transformation of the mole to melanoma.
I also read elsewhere that all moles can become cancerous, but moles with hair are less likely to do so. This is because such moles are almost certainly congenital nevi (singular: nevus), and ‘the hair indicates that the growth is way down in the skin, probably something that the person was born with’.