Atypical fibroxanthoma

Author: Vanessa Ngan, Staff Writer, 2005. Updated by Dr Ebtisam Elghblawi, Dermatologist, Tripoli, Libya, and DermNet NZ Editor in Chief, A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, November 2017. 

What is atypical fibroxanthoma?

Atypical fibroxanthoma (AFX) is a skin tumour that typically occurs on the head and neck of sun damaged older people.  The tumour-like growth should be considered a type of skin cancer but it may behave in a benign fashion.

A rare type of atypical fibroxanthoma occurs in younger patients on parts of the body that are not normally overexposed to the sun. These tumours are usually found on the trunk and extremities and tend to be larger and slower growing.

What causes atypical fibroxanthoma?

The development of atypical fibroxanthomas is associated with sun exposure and/or ionising radiation (X-rays). Both forms of radiation can cause abnormal growth of tumour cells called spindle cells. These are believed to come from fibrous cells in the dermis or from epidermal keratinocytes.

Who gets atypical fibroxanthoma?

Reports have shown an increased incidence of atypical fibroxanthoma in patients with acquired immune deficiency syndrome (AIDS) and in patients who are immune suppressed, for example because of organ transplantation.

Atypical fibroxanthoma affects both genders equally, with a mean age of 69 years at diagnosis.

What are the clinical features of atypical fibroxanthoma?

Atypical fibroxanthoma often appears in areas that have received excessive sun exposure, usually around the ears, nose, cheeks, and back of the neck, or in areas where individuals may have previously received radiotherapy treatment. They have also been reported to occur on the trunk, extremities, and in sun-protected areas.

Although rare, cutaneous metastases from atypical fibroxanthoma have been reported. 

How is atypical fibroxanthoma diagnosed?

Because atypical fibroxanthoma can look like other skin cancers, it is usually diagnosed by a pathologist after a skin biopsy or excision.

The diagnosis depends on finding large, pleomorphic, fibrocytic, spindle-shaped, anaplastic tumour cells haphazardly arranged in the dermis. Immunohistochemistry stains should be undertaken but may be nonspecific. Cytokeratin and melanoma stains are negative.

What is the differential diagnosis for atypical fibroxanthoma?

Other lesions to be considered in the differential include:

What is the treatment of atypical fibroxanthoma?

Atypical fibroxanthoma is treated by surgical excision. Small lesions may be removed by curettage. Mohs micrographic surgery is becoming the treatment of choice for large or recurrent lesions, as it reliably removes the complete tumour while sparing surrounding normal healthy tissue. They rarely recur.

How is atypical fibroxanthoma prevented?

Most cases of atypical fibroxanthoma could be prevented by avoiding excessive sun exposure. Patients should be advised to follow sun protection methods when outdoors.

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