Updated: Feb 18, 2019
#ReclaimYourPower with these facts about a mysterious disease.
🔬All of my posts are informational only and not meant to replace the advice of your physician. Do not make any change without first talking to your doctor. 🔬⠀
On Instagram I've read many misconceptions about melanoma. Here are some, hopefully debunked.
1) "Aren't all melanocytes bad?"
Melanocytes aren't bad. No part of our bodies is bad! But they are unique and sort of peculiar, a category unto themselves. They are everywhere in your body and actually - they are the good guys!
Melanocytes are born to move. They begin in utero along the neural crest and spread early in development along the ectoderm to find the skin and hair. They also migrate to other organs and tissues along the way. They are specialized cells whose entire function is protection (that's what I mean about being the good guys).
They have tentacles, long arms called dendrites, and in each arm are packages full of melanin granules. (Melanin itself is a molecule found in most animals. It colors insect shells dark and makes squid ink black.) When you expose yourself to UV light, production and packaging of these granules ramps up. These packages are transferred directly into neighboring keratinocytes (skin cells), where they physically shield the DNA in the nucleus from UV radiation that can cause mutations.
2) What a pre-melanoma is is not well-understood.
People, usually white people, have screening exams to check for moles that look atypical. Sometimes these moles that look atypical to the doctor are entirely benign and sometimes they are diagnosed as atypical nevi (sometimes called dysplastic nevi). But, these atypical moles are not currently understood to have the potential to develop into melanoma. Atypical moles are removed because they mimic melanoma - both to your dermatologist's eye and under the microscope. These lesions could harbor molecular alterations that would indicate they are on the path to melanoma. But we don't really know what an atypical nevus has the potential to develop into, nor do we know what came before a melanoma.
Atypical nevus ->->-> ???
???? ->->-> Melanoma
Research and molecular testing is leading us towards a precise idea of what is a pre-melanoma is. But the microscopic appearance is not the gold standard.
3) Melanoma is the smallest, deadliest disease.
When a malignancy stays within the original tissue we call it 'In-situ', Latin for in it's place. Once all tumors invade beyond their origin they can spread to other body parts.
What makes melanoma especially challenging is that we measure invasion for melanoma in 10ths of a millimeter. When a melanoma invades down through the skin surface and into the dermis we measure the depth of the tumor. A melanoma that invades at or greater than 0.8 mm is considered stage Ib and could be considered for sentinel lymph node biopsy. Invasion greater than 1 mm is considered deep.
4) Not all melanomas come from sun damage.
Melanomas are understood to arise along different paths (with some overlap). By this I mean that some root cause broad categories exist. Each of these has a separate molecular triggering event, separate anatomic location and different patterns of growth, both on the skin and under the microscope. They are all malignancies of melanocytes, but each is really a different disease:
Those on chronic sun damaged body parts are called lentigo maligna melanoma.
Those on non sun exposed parts, such as the trunk, are typically called superficial spreading type.
Those on palms of the hands and soles of the feet are called acral lentiginous melanoma.
Those on mucosal membranes (vaginal, anal and sinuses) are named for the anatomic location.
Melanoma of the pigmented cells of the eye (uveal).
5) Pigment has nothing to do with how a melanoma behaves.
Let's be clear that a dark and changing lesion on the skin needs to be looked at by a dermatologist. For completeness, I will take this opportunity to remark on the clinical features that are associated with melanoma. What should you look for when evaluating your moles?⠀
A Asymmetry (one half of the mole doesn't match the other). ⠀
B Border irregularity.
C Color that is not uniform.
D Diameter greater than 6 mm (about the size of a pencil eraser).
E Evolving size, shape or color.
(and, possibly add the Letter F, for something 'funny' or not quite right about a lesion).
Although a dark skin lesion is alarming, and should be looked at by a dermatologist, to me, the pathologist, pigment means nothing. Pigment can be seen in melanoma, benign nevi, seborrheic keratoses, basal cell carcinomas and even the decoy 'pigment' of broken down blood particles.
A melanoma is a malignancy of melanocytes, the cells that create and distribute melanin pigment. How much or how little pigment a melanoma has has nothing to do with how the melanoma will behave. Deadly melanomas can be without pigment, and heavily pigmented melanomas can be indolent (slow growing). The presence or absence of pigment isn’t included in the pathology report.
I can do another Melanoma Myth Buster. Do you have a question about Melanoma biology or diagnosis?
You might want to read my other three posts about Melanoma from a pathologist's perspective: