What is Dermatofibroma?
Dermatofibroma, also known as fibrous histiocytoma, is a common type of harmless skin lesion, or growth. They appear as firm bumps under the skin. The name ‘fibrous histiocytoma’ mainly describes what these bumps look like under the microscope, instead of indicating the type of cells they are made from. These bumps occur in the deeper layers of the skin, usually on arms and legs, and are often quite small, generally not larger than a centimeter in diameter. These skin bumps can be found across all age groups, but are more common in individuals between the ages of 20 to 50, especially in women.
Most dermatofibromas cause no symptoms, but they can sometimes cause pain, discomfort, or itchiness. They form from the overgrowth of fibroblasts, which are a type of cell that makes collagen, a protein that forms the structure of skin. Although the exact cause of dermatofibromas is unknown, they may appear after insect bites, minor injuries, or shallow puncture wounds. Even though dermatofibromas are harmless, they can sometimes come back in the same place. Even more rarely, they can spread to other parts of the body. So, when diagnosing these bumps, it’s important to distinguish them from a similar-looking but more aggressive skin cancer called dermatofibrosarcoma protuberans (DFSP).
What Causes Dermatofibroma?
Whether dermatofibroma is a reaction to something or an actual tumor is still unclear. We don’t know the exact cause yet, but often people with dermatofibroma have had some type of small injury to the area, like an insect bite, slight harm, or a prick from a rose thorn. However, not all patients report this and it’s only found in about one in five cases. Most of the time, dermatofibromas just appear without any injury or specific event happening first. They rarely go away on their own, which might mean that they are actually tumors rather than just a response to injury.
Dermatofibromas are made up of multiplying fibroblasts, which are cells that make up connective tissue in the body, often including involvement of histiocytes, a type of cell involved in the body’s immune response. Some studies have found unique markers in the cells of dermatofibromas that might suggest they are tumors. However, other studies suggest that dermatofibromas could be both a reaction and a tumor at the same time, with some parts potentially being a tumor and others being a response to injury.
Risk Factors and Frequency for Dermatofibroma
Dermatofibroma is a common skin condition that’s found in nearly all population groups, making up about 3% of all skin disease lab samples. However, getting a precise worldwide number is difficult since many people don’t have symptoms and might not go to the doctor. People typically develop these skin lesions when they’re in their 20s to 40s. Studies show it’s more common in females, but the rates can be similar or possibly twice as high in females compared to males.
- Dermatofibroma is a widespread skin issue found in almost all population groups.
- It accounts for roughly 3% of all skin disease lab tests.
- Much of the global incidence isn’t known because a lot of people are symptom-free and don’t seek medical help.
- People usually get these lesions when they’re between their 20s and 40s.
- Research indicates it’s more common in females, but the rate can be similar or up to twice as high as in males.
Signs and Symptoms of Dermatofibroma
Dermatofibromas are growths that develop slowly and can appear anywhere on the body, but they often occur on the arms and legs. They look like firm, non-painful lumps on the skin. Sometimes, these lumps may have a tan-pink or reddish-brown color. Usually, dermatofibromas are smaller than 1 cm, but some can grow larger than 3 cm.
Typically, these growths don’t cause any symptoms, but sometimes they might be itchy or sensitive to touch. Around one in five people with dermatofibromas have experienced a minor injury, such as an insect bite, in the same area. It’s important for doctors to thoroughly check the entire body during a skin exam, as multiple small growths might be present on the patient.
One key feature of a dermatofibroma is the “dimple sign.” This happens when applying pressure to the side of the lump causes the middle to indent, or “dimple.” It’s because the lump is tightly attached to the tissue beneath the skin.
While multiple dermatofibromas can occur, they’re often linked to specific situations. For example, they can be seen more often in people with autoimmune conditions who are receiving immune system-suppressing treatments, people who are HIV-positive, and pregnant women. Additionally, some people might inherit a genetic predisposition for multiple dermatofibromas.
Doctors typically diagnose dermatofibromas by their appearance and the patient’s medical history. Old growths should not have a history of rapid changes. Although it’s extremely uncommon, some benign dermatofibromas can metastasize, or spread to other parts of the body. These would usually be larger than the usual dermatofibromas and might exhibit features that are different from typical growths.
Rarely, one might develop multiple dermatofibromas clustering together, forming a patch of more than 15 individual skin lumps. This variant, which can be born with or develop suddenly, is often seen in children and young adults. These growths typically appear as reddish or darkened skin spots, and are usually found on the lower limbs.
Testing for Dermatofibroma
If a dermatologist suspects a skin problem called dermatofibroma, they’ll likely use a tool called a dermoscope which can show a white spot in the center of the lesion, surrounded by a darker, web-like pattern. Although this tool is helpful, a decisive diagnosis is usually made by removing a small portion of the lesion and examining it under a microscope. This is known as a histopathological examination.
Before removing any tissue for examination, a dermatologist might use soundwave imaging, also known as ultrasound or sonography. Dermatofibromas typically show up on these images as bloodless areas in the skin’s layers, often with some spiky edges that are not clearly defined. These findings on sonography often match well with the histopathological examination results in terms of size and borders.
Treatment Options for Dermatofibroma
Dermatofibromas usually don’t need treatment unless they’re causing problems. If the skin growth starts to change in looks or bleed, which can signal it becoming cancerous, it will need to be cut out and tested in a lab. The types of dermatofibromas that look unusual and don’t appear like the usual ones tend to come back more often and can rarely spread to other parts of the body. So it’s better to remove them completely to be safe.
If someone decides to have a dermatofibroma removed because they don’t like how it looks, they should know that the scar left behind could stand out more than the dermatofibroma, especially on the legs. Freezing therapy (cryotherapy) might be a good option if the dermatofibroma sticks out above the surface of the skin and gets bothered because of frequent bumps or scrapes.
What else can Dermatofibroma be?
Distinguishing benign skin growths known as dermatofibromas from more severe and aggressive skin changes that look similar is crucial. Some conditions can appear like dermatofibromas, but they have more severe consequences.
For instance, Dermatofibrosarcoma protuberans (DFSP) is a more aggressive skin condition that can look just like a harmless dermatofibroma. Early signs of DFSP may present as a firm, skin-colored lump that gets bigger slowly over time. To diagnose this, a microscopic examination of the skin tissues is required. It often involves a larger area under the skin and shows a distinctive ‘honeycomb’ pattern. DFSP also shows up differently in lab tests in contrast to benign dermatofibromas. For instance, DFSP will test positive for CD34 and not for factor XIIIa, whereas dermatofibromas will show opposite results. Also, the cell growth rate is much higher in DFSP compared to dermatofibromas.
Other skin conditions that can be confused with dermatofibromas include Kaposi sarcoma, intradermal nevi, keratoacanthomas, and basal cell carcinomas. Kaposi sarcoma is known for its unique cell growth style in the dermis (skin), and it tests positive for certain viruses. Intradermal nevi are softer than dermatofibromas and their skin doesn’t dimple when pinched. Keratoacanthomas grow rapidly and usually have a central plug made up of keratin. Lastly, basal cell carcinomas can look like dermatofibromas, especially when they have certain unique skin features like basaloid proliferation. Diagnosing these conditions accurately can be difficult, particularly in superficial biopsies that may miss the underlying skin change. Therefore, medical professionals must use specific tests and examinations to distinguish these conditions properly.
What to expect with Dermatofibroma
Dermatofibromas are harmless skin lesions with a very good chance of recovery. In some cases, these lesions can even disappear on their own, leaving behind skin that’s less pigmented. For the most part, dermatofibromas stay the same for a long time without significant changes.
These lesions hardly come back if thoroughly removed. However, more aggressive types can show a local recurrence in about 20% of patients. As a result, if the cellular or unusual types are found during removal, it might be necessary to do another removal for assurance due to the small chance of the lesion reappearing at the same place.
In very rare cases, the cancer spreading to other parts of the body has been reported.
Possible Complications When Diagnosed with Dermatofibroma
The main problems linked to dermatofibroma mostly come from the surgical removal. These problems can include bleeding, infection, and scarring or disfigurement. There might also be a need for extra procedures.
Possible complications:
- Bleeding
- Infection
- Scarring or disfigurement
- Need for additional procedures
Preventing Dermatofibroma
Patients should be made aware that dermatofibromas are harmless and don’t always need to be removed. Even though examinations of the skin, along with imaging studies and medical history, can indicate a dermatofibroma, the only way to confirm this is through a pathological examination. Additionally, it’s very important to consider what the patient wants when deciding whether to remove these skin changes or just keep an eye on them.
