Atypical fibroxanthoma: a histological and immunohistochemical review of 171 cases.

Cutaneous Pathology, Western Australia, Australia.
The American Journal of dermatopathology (Impact Factor: 1.3). 08/2010; 32(6):533-40. DOI: 10.1097/DAD.0b013e3181c80b97
Source: PubMed

ABSTRACT The clinical and histological features of 171 atypical fibroxanthomas (AFX) from a single institution in Western Australia are outlined. This area experiences high levels of solar radiation, and all assessable biopsies showed solar elastosis. Patients were aged between 41 and 97 years (median age 74), with 76% of tumors occurring in men (male to female ratio approximately 3 to 1). Most tumors were small, with a median diameter of 10 mm and a range of 4-35 mm. Only 5% exceeded 20 mm in diameter. Most AFX were well-circumscribed dermal lesions, with limited invasion of subcutis in a minority. Histological variants identified included keloidal (n = 8), clear cell (n = 3), and granular cell (n = 3), plaque like (n = 4), and myxoid (n = 1). Bland cytological appearances (spindle cell nonpleomorphic AFX) were noted in 5 tumors, with osteoclast-like giant cells in 2. Features suggesting regression were present in 22 cases. Two cases recurred locally, none metastasized. No tumors expressed melanocytic or epithelial markers. Seventy-four percent of cases expressed smooth muscle actin, typically strongly and diffusely. No AFX stained with desmin. Only 1 of 50 cases was CD117 positive. In conclusion, AFX may show a wide range of histological appearances, and a panel of immunohistochemical markers is essential to make the correct diagnosis. Histological mimics, such as poorly differentiated squamous cell carcinoma, must be carefully excluded. Specific diagnosis is important because there seems to be a very low risk of recurrence or metastasis despite the frequently alarming histology.

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    ABSTRACT: : Atypical fibroxanthoma (AFX) is a dermal mesenchymal neoplasm arising in sun-damaged skin, primarily of the head and neck region of older men. Conservative excision cures most. However, varying degrees of subcutaneous involvement can lead to a more aggressive course and rare metastases. Thus, AFX involving the subcutis are termed pleomorphic dermal sarcomas or other monikers by some to recognize the more threatening natural history. We reviewed cases of "metastatic AFX" from our institution and from the files of a consultative dermatopathology practice. Nine of 152 patients with AFX were identified at a single institution (2000-2011). Two additional patients were identified from the files of a consultative practice. Clinical, radiological, and pathological features were reviewed and cases with histologically verified metastases identified. Median age was 67 (range, 45-91) years, all male, and involving the head and neck region. Two cases had no documented involvement of the subcutis, and 2 cases had only superficial subcutis involvement. Median time to metastases was 13 (range, 8-49) months. Three patients developed solitary regional lymph node metastases while 8 had widespread metastases. Five patients developed local recurrence within 8 months, and all 5 developed widespread metastasis. With median follow-up of 26 (range, 10-145) months, 6 died of disease (median, 19 months; range, 10-35 months), 4 were alive and well, and 1 was alive with disease. AFX has very rare metastatic potential, even those without or with minimal subcutis involvement, and can lead to mortality. Most metastasis and local recurrence occurred within 1 year of presentation. Solitary regional metastases were associated with better outcomes than those with multiple distant metastases. Patients with repeated local recurrences portended more aggressive disease including development of distant metastases.
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    ABSTRACT: Poorly differentiated, cytologically malignant, spindle cell neoplasms of the skin may present a diagnostic challenge with important clinical consequences. In particular, the distinction between poorly differentiated cutaneous spindle cell squamous cell carcinoma (SpSCC) and atypical fibroxanthoma (AFX) remains controversial, but with important clinical implications: SpSCC exhibits an increased tendency for both local recurrence and metastasis compared with AFX. AFX is generally accepted as a diagnosis of exclusion based on negativity for a broad panel of immunohistochemical markers, including multiple cytokeratins, melanocytic markers, muscle markers, and vascular markers. As cytokeratins can also be occasionally lost in SpSCC, it would be of tremendous diagnostic value if there were additional specific markers to facilitate the distinction of lineage in this differential diagnostic context. Initial studies demonstrated p63 to be of utility in distinguishing AFX from SpSCC; however, p63 has proved to lack specificity, as it also exhibits variable reactivity in a subset of AFX. Recent studies have shown p40 immunohistochemistry to be a more specific marker than p63 for the designation of squamous differentiation in carcinomas involving other organ systems. In the current study, we define the utility of p40 immunohistochemistry among common cutaneous spindle cell malignancies, and, specifically, we compare the diagnostic accuracy of p40 and p63 in distinguishing AFX from SpSCC. We show that p40 and p63 exhibit comparable sensitivity, but p40 exhibits superior specificity in the distinction of AFX from SpSCC.
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May 28, 2014