Dermatofibroma: Pathophysiology

00:01 Welcome. With this talk, we're going to cover a benign lesion that occurs within the dermis.

00:07 It's actually very aptly named.

00:09 It's a dermato, so within the dermis fibroma fibrous connective tissue and it's a benign tumor, it's an oma.

00:17 So there we go. So dermatofibromas are benign skin tumors.

00:21 They appear as firm raised nodules.

00:24 They're often red or brown.

00:26 They're typically found in the lower legs although they can be anywhere.

00:31 The epidemiology is it's the typical peak incidence is 20 to 40 years of age. There is a female predominance.

00:39 Um, and some of that may be estrogen-related , but it's not entirely so.

00:45 Pathophysiology. Uh, it's not well understood.

00:48 We know that this is almost certainly a reactive process secondary to some local trauma, such as an insect bite or some other small incidental trauma. So in that way it may be kind of analogous to a keloid, although there felt to be very different.

01:05 It's spontaneous and it's almost always invariably benign.

01:09 So there's local trauma.

01:11 That injury leads to local inflammation.

01:14 But then we get fibroblasts and histiocytes that are proliferating in that region.

01:18 That's the appropriate response to injury.

01:21 Those fibroblasts will have increased collagen production.

01:24 And then we get a nodule that forms in the dermis.

01:27 Now you saw that lesion.

01:29 And we'll get back to what it looks like grossly in a minute.

01:32 Looks like it's raised well.

01:33 It's raised because of the kind of the material that's underneath it in the dermis pushing it up. The epithelium is entirely normal.

01:41 So the clinical presentation you get these firm raised nodules.

01:45 They can be various colors depending on the degree of pigmentation and how much vasculature is in them.

01:50 Often quite asymptomatic.

01:52 But if there's any inflammation in them or if you rub them, they can become itchy or tender.

01:57 They're generally small, less than a centimeter, and they often have a little dimpled center, particularly if you kind of push them together if you pucker them multiple dermatofibromas.

02:08 So in the neighborhood of greater than 15, lesions may be associated with autoimmune diseases or malignancies.

02:15 So if you have a patient with several you may want to look for an occult cancer. The diagnosis.

02:22 So it's the clinical appearance.

02:24 But then you can nail it with the appropriate biopsy.

02:28 So this is a low power.

02:29 And as you look at this at low power the epidermis on the top completely normal.

02:34 There's nothing different about that.

02:36 But there is this kind of vague pink purple bluish region in the middle down in the dermis.

02:43 That's what's being circled.

02:44 And that's what we would want to get on biopsy to confirm our diagnosis.

02:48 And in there we're going to see mostly fibroblasts laying down collagen and a kind of a and a sparse inflammatory infiltrate mostly composed of macrophages otherwise known as Histiocytes.

03:01 They're uniform spindle cells.

03:03 So the fibroblasts are not atypical.

03:05 They are not they are not in any way acquiring mutations. They're just simply proliferating as a response to probably to injury. The lesions are separated from the overlying epidermis by a clear Grenz or border zone. Grenz is German.

03:22 Presence. There's a variable amount of mononuclear infiltrate, like I said, and the collagen fibers may be trapped around the periphery of the lesion.

03:31 It's kind of expansile, so they compress the surrounding normal dermis. How do you manage these? Well, not much to be done.

03:40 You can observe them. They have essentially zero malignant potential.

03:44 If the patient wants them removed.

03:46 It's pretty easy to do so just with a surgical excision.

03:50 You can also, if you want treat them with liquid nitrogen.

03:54 And with that we've covered dermatofibromas a lesion that pretty much says what it is.