Atypical fibroxanthoma (AFX) of the skin is a low-grade malignancy related to

malignant fibrous histiocytoma Undifferentiated pleomorphic sarcoma (UPS), also termed pleomorphic myofibrosarcoma, high-grade myofibroblastic sarcoma, and high-grade myofibrosarcoma, is characterized by the World Health Organization (WHO) as a rare, poorly differentiated neopl ...

, which it resembles

histologically Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

.James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. . Atypical fibroxanthoma manifests as a hard, pink or red

papule A papule is a small, well-defined bump in the skin lesion, skin. It may have a rounded, pointed or flat top, and may have a umbilication, dip. It can appear with a Peduncle (anatomy), stalk, be thread-like or look warty. It can be soft or firm a ...

nodule Nodule may refer to: * Nodule (geology), a small rock or mineral cluster * Manganese nodule, a metallic concretion found on the seafloor *Nodule (medicine), a small aggregation of cells *Root nodule Root nodules are found on the roots of plants, ...

that grows over the course of several months and may bleed or ulcerate. They typically occur on the head and neck. Atypical fibroxanthoma is usually asymptomatic. The exact cause of atypical fibroxanthoma is unknown. They may originate from

myofibroblasts A myofibroblast is a cell phenotype that was first described as being in a state between a fibroblast and a smooth muscle cell. Structure Myofibroblasts are contractile web-like fusiform cells that are identifiable by their expression of α-s ...

Ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

and sun exposure are most likely risk factors. Atypical fibroxanthoma has also been associated with

P53 p53, also known as tumor protein p53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory transcription factor protein that is often mutated in human cancers. The p53 proteins (originally thou ...

mutations,

xeroderma pigmentosum Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in su ...

radiation therapy Radiation therapy or radiotherapy (RT, RTx, or XRT) is a therapy, treatment using ionizing radiation, generally provided as part of treatment of cancer, cancer therapy to either kill or control the growth of malignancy, malignant cell (biology), ...

, trauma, and

immunosuppression Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse react ...

. Because atypical fibroxanthoma is an uncommon condition that can mimic other disorders,

skin biopsy Skin biopsy is a biopsy technique in which a skin lesion is removed to be sent to a pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 day ...

is used to make the diagnosis. Treatment involves surgical excision. Atypical fibroxanthoma is more common in men than women and usually appears in the seventh or eighth decade of life.

Signs and symptoms

Atypical fibroxanthoma (AFX) often manifests as a single, hard, pink or red

that swells over several months and has the potential to bleed or ulcerate. Tumors typically have a diameter of less than 2 cm, while they can occasionally be as large as several centimeters. There have been reports of an uncommon pigmented type of AFX. The most frequent locations for AFX are the head and neck. Less frequently occurring tumors of the trunk and extremities may appear as bigger tumors. Sites like the

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

or eyelid are rarely impacted. The majority of AFX tumors don't cause any symptoms. Rarely the lesion may be tender. It is rare to experience

pruritus An itch (also known as pruritus) is a sensation that causes a strong desire or reflex to scratch. Itches have resisted many attempts to be classified as any one type of sensory experience. Itches have many similarities to pain, and while both ...

Causes

It is unclear what causes atypical fibroxanthomas. It is thought to originate from

or cells that resemble

fibroblasts A fibroblast is a type of biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibrobla ...

. Since the majority of lesions form on White patients' sun-exposed heads and necks,

ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

appears to be important. In AFX,

mutations as well as cyclobutane pyrimidine dimers, UV photoproducts implicated in the development of

skin cancer Skin cancers are cancers that arise from the Human skin, skin. They are due to the development of abnormal cells (biology), cells that have the ability to invade or metastasis, spread to other parts of the body. It occurs when skin cells grow ...

, have been found. AFX has been observed in children with

. There have been other hypothesized causes of AFX, such as

, burns, and trauma.

Diagnosis

Since atypical fibroxanthoma is an uncommon disorder that mimics amelanotic melanomas, Merkel cell carcinomas, and basal and

squamous cell carcinomas Squamous-cell carcinoma (SCC), also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in Epithelium#Cell types, squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in ...

clinically, a

is the gold standard for diagnosis. Atypical fibroxanthoma (AFX) is frequently found to have a well-circumscribed, nonencapsulated dermal tumor that is either contiguous with the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

or separated from it by a narrow zone of

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

(Grenz zone); plump

spindle cells Von Economo neurons, also called spindle neurons, are a specific class of mammalian cortical neurons characterized by a large spindle-shaped soma (or body) gradually tapering into a single apical axon (the ramification that ''transmits'' si ...

with prominent nuclei, epithelioid cells, and multinucleated giant cells; atypical

mitoses Mitosis () is a part of the cell cycle in eukaryotic cells in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the ...

and severe cellular pleomorphism; and varying presence of thin or ulcerated

or peripheral epidermal collarette.

Treatment

For atypical fibroxanthoma, surgical excision is the preferred course of treatment. This was done with 1 cm margins in the past, but

Mohs micrographic surgery Mohs surgery, developed in 1938 by general surgeon Frederic E. Mohs, is microscopically controlled surgery used to treat both common and rare types of skin cancer. During the surgery, after each removal of tissue and while the patient waits, the ...

and routine follow-up have become the norm, with recurrence rates ranging from 0.0% to 6.9%.

Epidemiology

Men are more likely to experience AFX than women, and it often affects adults in their seventh or eighth decade of life. While AFX can affect people of any ethnicity, non-

Hispanic The term Hispanic () are people, Spanish culture, cultures, or countries related to Spain, the Spanish language, or broadly. In some contexts, Hispanic and Latino Americans, especially within the United States, "Hispanic" is used as an Ethnici ...

White people have been the majority of those with reported instances. Patients with AFX frequently have a personal history of previous

basal cell A basal cell is a general cell type that is present in many forms of epithelial tissue throughout the body. Basal cells are located between the basement membrane and the remainder of the epithelium, effectively functioning as an anchor for the epi ...

squamous cell cancer Squamous-cell carcinoma (SCC), also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...

References

External links

DermNet

{{Soft tissue tumors and sarcomas Dermal and subcutaneous growths