Transcription
In this video, we'll consider sebaceous hypoplasia. What it is, how to diagnose it using a dermoscope, and why they matter. Training a primary care [Music] dermoscopist. Academy where we help you become the great primary care dermoscopist.
Hypoplasia? Well, it's hyperplasia of the sebaceous gland attached to the hair follicle. Not sure what else to say, really. Oh, yes, to tell you more, let's have a quick look at this model of the skin. Quick orientation. Here's the skin surface. This is the epidermis. This is the dermis. And here you've got the dermo-epidermal junction, the basement membrane there. Note this pilo-sebaceous unit, as it's called. Their hair, the sebum gland, the bulb, and the erector pili muscle attached to the hair. It's a holocrine gland attached to a common excretory duct that's associated with the particular hair follicle.
What does this do? It produces sebum, which protects and hydrates the skin surface and has mild anti-staphylococcal and anti-inflammatory properties. This view is sagittal, and it's not the angle we see when using a dermoscope. Therefore, let's take a cross-section in this direction here and put it under a microscope. And this is what you see. Note the glands, the central hair follicle, and attached muscle. In sebaceous hyperplasia, the sebaceous glands are normally structured but increased in number. It's a benign tumor.
What does sebaceous hypoplasia look like on a patient's skin? They're found mainly on the face, nose, cheeks, and forehead. They can be between 2 to 9 mm in size, often soft and yellow-white or even skin-colored papules. Some have a central umbilication due to a widened hair follicle infundibulum. How common are they? Middle-aged and elderly patients, with surveys showing approximately 1% of people will have them, and many people don't know that they are there. Sometimes they're solitary, but they can be in clusters, and when you start looking using a dermoscope, you will find them on your patients. More men than women tend to have them, and at an average of 50, they can be seen from the age of 30 onwards.
So, what do we see on dermoscopy? There are three things to look out for. The most common dermoscopic feature are these white, yellowish, lobulated structures, grouped white globules, or clots, if you prefer, corresponding to the sebaceous lobules. How would you describe them? The second feature to look out for on dermoscopy is a central umbilicated area, detected in 60% of cases, correlating to a centrally dilated follicular infundibulum. And don't say that in a hurry. The third key feature you will hear about are crown vessels. What exactly are crown vessels? Well, let me show you. Here's my crown I made earlier. It's red because they are composed of blood vessels. This is how you will see them through a dermoscope. This is where there is a red ring of vessels around, with vessels radiating in towards the center, poking in towards that middle part. These vessels, however, do not cross the center line, or you'll need to think carefully about another diagnosis, such as a BCC. Crown vessels are a feature I don't see very often, and in one series, crown vessels were seen in only one in three sebaceous hyperplasias, whereas irregular linear vessels were observed on 60%. So don't let the fact that you can't see a crown put you off. Short stopy vessels are far more common.
You know what? I feel hungry suddenly, for some reason. I tell you what, let's make an edible model because, why wouldn't you? First, we need a widened infundibulum of the hair follicle. What do you think? A Hobnob or a Crunch Cream? I'm more a Crunch Cream kind of guy, so let's go for that. Then you add a few hypertrophic sebaceous glands. It's difficult to get hold of sebaceous glands at this time of year, so I've opted for marshmallows instead. Crown of thorns, you'll see if you're lucky. You're more likely to see these short, linear, irregular vessels, and I prefer them because they're edible. And there you have it, one tasty sebaceous hypoplasia, ready for eating. What you don't want to see are vessels crossing the midline, even if they are strawberry laces.
Why does sebaceous gland hyperplasia matter? Firstly, because patients present with them for cosmetic reasons. However, treatments are destructive and often cause scarring and depigmentation due to the location of most of the gland being in the dermis. Recurrence is common, and I don't treat them. Secondly, they can confuse people by looking like a BCC. Learning to recognize sebaceous gland hyperplasia confidently means you can rule out a BCC and avoid an unnecessary referral. Reassure your patient, explaining to them what the problem is.
Let me present to you now two patients for you to think about. This 82-year-old gentleman came with this 6 to 7 mm thing papule on his sternal notch area. He'd noticed it two months previously. It had no pain or bleeding. He'd had no previous skin cancers. It was firm with a rolled-looking edge, and my initial thought was that it was a small BCC. However, looking through the dermoscope, this is what I saw: white lobules, a couple of yellowish-brown centers with an eye of faith, the best crown of thorns I'd seen up to that time. It was early in my dermoscopic career, and I was keen to see if I could trust my dermoscopic eye. He consented to allow me to remove it for him, and histology confirmed this was a sebaceous gland hyperplasia.
Patient two is a 35-year-old with an 18-month history of this slowly growing pink papule on her forehead. There was a central depression, suggestion of some vessels, and I was thinking maybe this is a BCC. Here's the dermoscope, and these vessels we call arborizing or branching, thin and well-focused because they are located in the epidermis and thus higher up and more superficial. Note these yellow-white dots. These reminding me of sebaceous gland hyperplasia. Is that vessel crossing the middle, however? But no, the vessels are radiating from the edge into the middle, which I thought was similar to what sebaceous gland hyperplasia sometimes do. This is a polarized view. Switching to a non-polarized view, and look, there are white dots that appear. When we talk about BCCs in another video, we'll mention milia-like cysts, which are calcium deposits. Remind me, what's the first rule of GP dermoscopy? If in doubt, refer it out. Could I rule out a BCC here? No. Heard her with all these photographs urgently to my local dermatological department. After 3 months, she didn't have an appointment and chose to go privately instead and have it removed. On histology, this was a... now have a guess... a desmoplastic trichoepithelioma. Yeah, exactly. It's a benign hamartoma of the cells lining the hair follicle. Now, I've seen one or two, and we'll probably never see another one.
So, what should we put on the shelf behind me to remind us of sebaceous gland hyperplasia? The marshmallows won't last, so it will have to be this crown of thorns. There you go. Training a primary care dermoscopist for every general [Music] practice.