What is Atypical Fibroxanthoma?
Atypical fibroxanthoma is an uncommon, mild form of skin cancer that often appears as a red lump or patch. This condition is a milder form of another cancer called undifferentiated pleomorphic sarcoma, previously known as malignant fibrous histiocytoma. Even though atypical fibroxanthoma shares many of the same characteristics with undifferentiated pleomorphic sarcoma under the microscope, its effects are less severe.
What Causes Atypical Fibroxanthoma?
The exact causes of atypical fibroxanthomas are not fully understood. Some scientists think that they may develop from a type of cell in the body known as myofibroblasts, or fibroblast-like cells. Sun exposure seems to be a key factor, as most of these skin growths are seen on the parts of the body often exposed to the sun, especially the head and neck of people with light skin.
Genetics also plays a role in the development of atypical fibroxanthomas, as they share some genetic changes with another type of skin cancer called undifferentiated pleomorphic sarcomas. This includes deletions in chromosomes 9p and 13q. But undifferentiated pleomorphic sarcomas tend to have more genetic alterations and are usually more aggressive.
Other things that might increase the risk of developing atypical fibroxanthomas include injuries to the skin, radiation treatments, and conditions that weaken the immune system, like diabetes, HIV, or having an organ transplant.
Risk Factors and Frequency for Atypical Fibroxanthoma
Atypical fibroxanthomas are most often found on the head and neck of older Caucasian individuals. However, they can also occur on the torso, shoulders, upper arms, and backs of the hands. Oddly enough, when these growths appear on the trunk and limbs, they tend to do so in younger people (average age 39), as opposed to when they’re found on the head and neck of older individuals (average age 69).
One study of 171 cases in Western Australia found that the age of patients could range from 41 to 97 years old, with an average age of 74. Interestingly, 76% of these tumors happened in men. Some patients as young as 13 have been diagnosed with atypical fibroxanthoma. This is especially true for those with medical conditions that predispose them to such growths, like Li-Fraumeni syndrome and xeroderma pigmentosum.
The rate of these tumors seems to be higher in people with weakened immune systems. For example, there’s an estimated incidence of 78 per 100,000 in patients who have had an organ transplant.
Signs and Symptoms of Atypical Fibroxanthoma
Atypical fibroxanthomas are skin growths that typically appear as small, well-defined red or pink lumps or raised areas of skin. Often, these may have a crusty or scaly surface, and sometimes they may have ulcers. These growths are usually small, with most measuring about 1 cm in diameter, and only a very small proportion are larger than 2 cm. These non-painful, non-itchy growths commonly develop quickly and mostly appear on the head and neck. However, some cases may be found on the arms, legs, or torso.
Examination of these skin growths through a dermatoscope (a specialized magnifying tool) shows a variety of blood vessels leading to the center of the growth, with white areas in between. There are many different conditions that these growths could be, such as various forms of skin cancer (basal cell carcinoma, squamous cell carcinoma, Merkel cell carcinoma, amelanotic melanoma) and other skin growths (leiomyosarcoma, atypical dermatofibroma, pleomorphic dermal sarcomas). In rare cases, they could also be a sign of cancer spreading from other parts of the body.
It’s worth noting that compared to atypical fibroxanthoma, pleomorphic dermal sarcomas are generally larger in size and have a higher chance of returning and spreading to other parts of the body.
Testing for Atypical Fibroxanthoma
Atypical fibroxanthoma is a rare skin condition that can look a lot like more common skin cancers like basal and squamous cell carcinomas, Merkel cell carcinomas, and non-pigmented melanomas. Usually, a skin biopsy is used to definitively diagnose this condition.
Alongside the biopsy, a diagnostic test called immunohistochemistry is often used. This test is completed on a small piece of tissue taken during the biopsy and can help confirm the diagnosis.
If the atypical fibroxanthoma has spread or is located in hard-to-reach areas, such as under the fingernails, a Magnetic Resonance Imaging (MRI) scan may be conducted. This scan shows a unique pattern or signal when it comes to atypical fibroxanthoma – the signal tends to be medium strength on T1 and T2-weighted images, which is in contrast to the high signal intensity seen in squamous cell carcinoma and melanoma.
Treatment Options for Atypical Fibroxanthoma
Atypical fibroxanthoma, a type of skin tumor, is not commonly dangerous as it rarely spreads to other parts of the body, and returns only in about 6% to 10% of cases. Certain risk factors can increase the chance of these tumors spreading, such as: having a weakened immune system, the depth of the tumor, the tumor spreading to blood vessels or nerves, and the presence of cell death within the tumor. If the cancer does spread, it most commonly affects the parotid gland (a major salivary gland), lymph nodes, and the layer of fatty tissue beneath the skin. When spreading occurs, it usually becomes apparent 12 to 24 months after the initial diagnosis.
The main treatment for atypical fibroxanthoma is surgical removal. In the past, doctors would typically remove the tumor as well as 1 cm of tissue surrounding it. Nowadays, the standard treatment is a surgical technique called Mohs micrographic surgery, followed by regular check-ups. This treatment method has low recurrence rates, between 0.0% and 6.9%.
For patients who are not suitable for surgery, electronic brachytherapy can be a successful treatment option. This is a type of radiotherapy that can be more effective if the tumor is reduced in size before treatment. Additionally, the treatment method of electrodesiccation and curettage, which involves using electricity to dry out and then scrape off the lesion, may be appropriate for slow-growing lesions smaller than 1 cm.
What else can Atypical Fibroxanthoma be?
When trying to diagnose atypical fibroxanthoma, or an unusual skin growth, doctors need to consider several other conditions that may look similar. These include:
- Amelanotic melanoma (a type of skin cancer without pigment)
- Basal cell carcinoma (the most common type of skin cancer)
- Dermatofibroma with monster cell (a type of benign skin growth)
- Leiomyosarcoma (a rare cancer of the smooth muscle)
- Undifferentiated pleomorphic sarcoma (a type of soft tissue cancer)
- Melanoma (a dangerous form of skin cancer)
- Merkel cell carcinoma (a rare and aggressive type of skin cancer)
- Neurothekeoma (a benign skin tumor)
- Pleomorphic dermal sarcoma (a subtype of skin cancer)
Doctors carefully compare the patient’s symptoms and test results with these conditions to accurately diagnose their problem.
What to expect with Atypical Fibroxanthoma
Atypical fibroxanthoma is a type of low-grade sarcoma that tends to appear on sun-exposed areas of the head and neck in older individuals. Generally, the outlook is positive, especially when the primary tumor is thoroughly removed. Nonetheless, around 5% of cases might see the tumor returning.
Possible Complications When Diagnosed with Atypical Fibroxanthoma
When properly treated through appropriate removal, Atypical Fibroxanthoma, a type of skin cancer, usually doesn’t lead to complications. However, in certain cases, it can lead to significant hardening of tissues. Very rarely, it can spread to other parts of the body.
