Welcome to the next chapter on actinic keratosis squamous a carcinoma in Bowen's disease. I would like to work through this chapter with you. First of all we will have a look at healthy skin in order to be able to recognize actinic keratosis. So what do we have in healthy skin? First of all we have a very regular entrance signal which you can see here of the same homogeneous structure which looks the same everywhere. You have a very thin horny layer, the stratum corneum and an underlying epidermis which is usually somewhat darker than the lighter papillary dermis and then you have the darker signal poorer reticular dermis in which you also find the blood vessels. The dermis joins the epidermis but is separated from it by the dermoepidermal junctional zone which is such a tiny little line that runs through the hair quite regularly. In the dermis which I already mentioned you can find the elongated dark blood vessels which are nicely visible. In actinic skin a clear hyperkeratosis is visible and accordingly an irregular entrance signal. One finds here a broader epidermis and also a broader horny layer as well as a clearly deeper demarcated dermoepidermal junctional zone as one can see here. There is also an irregular layering of the skin compared to healthy skin and blood vessels can also be seen here. So what is typical for actinic keratosis? You will see this in more detail later in the OCT images. We have here these dots and streaks and these white stripes are a very important criterion which can be often found in actaric keratosis in the literature. However these white streaks and dots are not quite specific as you can see here in this table. Sometimes they are also found in basal cell carcinoma in some lesions but much more frequently in actinic keratosis. This table is quite good so you have an overview of the structures and can assign them again well. Let's move on to the next topic. How do I distinguish actinic keratosis from invasive squamous cell carcinoma? First of all let's repeat the criteria of actinic keratosis. Here we have a hyperkeratosis, irregular entrance signal, a broadened epidermis, irregular layering, streaks and dots that we'll look at again in a moment and dilated blood vessels. In squamous cell carcinoma on the other hand there is no dermoepidermal junctional zone or only one that is very poorly demarcated, a very irregular broadened epidermis and bright horn cyst-like structures. They are quite typical and you can see them very well. In actinic keratosis we repeat it again on the image. We have a hyperkeratosis here, the thickening and also the thickening here. Furthermore you see a clearly thickened epidermis and a very irregular entrance signal along with that an irregular layering of the skin. Due to the hyperkeratosis, which is very strong at this point, there is an underlying signal shadow something like maybe from sonography and underneath unfortunately often not so much can be seen. Here in this case it is still a see-through shadow. You can try to trace the very broad but still well demarcated dermoepidermal junction zone and you can still see it here under the shadow but sometimes it's hard to do so. You also have dilated blood vessels and overall the thickened epidermis. In the next picture you start at the top with the hyperkeratosis here and an irregular layering of the skin, a clearly broadened epidermis as you can see here and a preserved dermoepidermal junctional zone which you can still trace and you can already see here the signal shadow which is stronger than in the image above but you can still see it that it's continuing here. You can also see the dots and the streaks which I was talking about earlier that are typical for actinic keratosis. Compared to dermoscopy the criteria of an actinic keratosis can also be found in OCT. For example like blood vessels can also be seen here in dermoscopy and in OCT and you also have this rough hyperkeratotic surface that also shows up in OCT with hyperkeratosis and an irregular entrance signal. Streaks and dots can also be seen very nice in this image. This is all together how an actinic keratosis looks like in OCT. However we need to look again more closely in this image. We have a massively thickened stratum corneum and you also have a very pronounced signal shadow in this area, a smaller one in this area and a bigger one in this area and if you want to go through now where the dermoepidermal junction is, it's very difficult because you can't tell exactly where it ends now. Here you could still recognize it but then well it becomes difficult. Here you see such a dark cone going down. This is a tumor infiltrate and so this is not just an actinic keratosis but already one transitioning into a squamous cell carcinoma. A squamous cell carcinoma like this can of course already be recognized clinically as in this picture but how does it look in OCT? And I would like to show you that. You have here these very bright horn cyst like areas which are quite typical for a squamous cell carcinoma and you have a very irregular broadened epidermis here. It is very difficult to say where it ends and one thinks it could still be here but then one does not know exactly. You can see blood vessels here and here and here and a dermoepidermal junctional zone that you can really follow with your finger is here not present and from this point on if you can no longer follow it properly you have a squamous cell carcinoma by definition. Let's now move on to Bowen's disease. I would like to show you a beautiful graphic by Professor Zalaudek. She examined actinic keratosis, Bowen's disease and squamous cell carcinoma in dermoscopy and you can see the strawberry pattern here in actinic keratosis in dermoscopy and in Bowen's disease these yellow opaque like structures in the center surrounded by small dotted vessels and also these small dotted vessels can be visualized in dynamic OCT. Dynamic OCT means that blood flow signals can also be visualized here. In squamous cell carcinoma just like in actinic keratosis there is a completely different vascular pattern. This is a very nice dermoscopic image of Bowen's disease where the dotted vessels can be seen very well and as you can see it looks the same in dynamic OCT. This is what Bowen's disease looks like in normal structural OCT. You have a hyperkeratosis and an already irregular entrance signal with a broadened epidermis. You have a broadened red ridges and a very plump and broad papillary body in between that you can see here. This is the typical homogeneous picture of a Bowen's disease. So here again the criteria of Bowen's disease are summarized. Hyperkeratosis, an irregular entrance signal, a broadened epidermis, the acanthosis, elongated red ridges and a plump broadened papillary dermis are the typical criteria of Bowen's disease. In Bowen carcinoma which is a very extensive tumor here you have a Bowen-like portion in this area with the dotted vessels which you can see here in the moscopy and on this area it's already ulcerated and hemorrhaged. When we take a closer look at this Bowen carcinoma in OCT again this is very similar to the squamous head carcinoma since Bowen carcinoma per se is a category of squamous head carcinoma. White horn cyst-like structures can also be seen here and a dilated blood vessel as well but we also have here a poorly demarcated dermoepidermal junction zone and you can still follow it here in this area and then here it becomes impossible. You have a very broad irregular epidermis and you can no longer tell exactly where it ends. And so in summary you are dealing with a large tumor a squamous head carcinoma. With this slide we have reached the end of this chapter and I thank you very very much for your time and your attention. Bye bye!

actinic keratosis

Bowen's disease

squamous cell carcinoma

OCT images

dermoscopy