Dermatofibroma

Template:Infobox medical condition (new) A dermatofibroma, or benign fibrous histiocytomas, is a benign nodule in the skin, typically on the legs, elbows or chest of an adult.<ref name=Andrew2020>Template:Cite book</ref> It is usually painless.<ref name=Andrew2020/>

It usually ranges from 0.2 to 2 cm in size but larger examples have been reported.<ref name=Andrew2020/> It typically results from mild trauma such as an insect bite.<ref name=Andrew2020/> Risk factors for developing multiple dermatofibromas include lupus, HIV, blood cancer and some medicines that weaken immunity.<ref name=Andrew2020/>

It is usually diagnosed by its appearance, but a biopsy may be required.<ref name=Andrew2020/> Other bumps such as granular cell tumor, melanoma, clear cell acanthoma and dermatofibrosis lenticularis disseminata may look similar.<ref name=Andrew2020/> Usually no treatment is needed.<ref name=Andrew2020/> It can remain unchanged for years but can resolve spontaneously.<ref name=Andrew2020/>

Signs and symptoms

Dermatofibromas<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> are hard solitary slow-growing papules (rounded bumps) that appear in a variety of colours, usually brownish to tan. They are often elevated or pedunculated. A dermatofibroma is associated with the dimple sign; by applying lateral pressure, there is a central depression of the dermatofibroma. Although typical dermatofibromas cause little or no discomfort, itching and tenderness can occur. Dermatofibromas can be found anywhere on the body, but most often they are found on the legs and arms.<ref>Template:DorlandsDict</ref> They occur more often in women; the male to female ratio is about 1:4.<ref name=pierson/> The age group in which they most commonly occur is 20 to 45 years.

Some physicians and researchers believe dermatofibromas form as a reaction to previous injuries such as insect bites or thorn pricks.<ref name="pierson">Template:EMedicine</ref> They are composed of disordered collagen laid down by fibroblasts. Dermatofibromas are classed as benign skin lesions, meaning they are completely harmless, though they may be confused with a variety of subcutaneous tumours.<ref>Template:Cite journal</ref> Deep penetrating dermatofibromas may be difficult to distinguish, even histologically, from rare malignant fibrohistocytic tumours like dermatofibrosarcoma protuberans.<ref name="pmid16740036">Template:Cite journal</ref>

Dermatofibromas typically have a positive buttonhole sign, or central dimpling in the center.<ref name="Boursicot2013">Template:Cite book</ref>

Diagnosis

Immunohistochemical staining

Neoplasm	CD34<ref name="Bolognia" />	Stromelysin-3<ref>Template:Cite journal</ref>	Factor XIIIa<ref name="pierson"/>
Dermatofibroma	-	+	+
Dermatofibrosarcoma protuberans	+	-	-

See also

• Acrochordon, also called skin tags
• Dermatology
• List of cutaneous conditions
• Seborrheic keratosis