Atypical Fibroxanthoma: A Histological and Immunohistochemical Review of 171 Cases

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.

Superficial CD34-positive fibroblastic tumor: report of 18 cases of a distinctive low-grade mesenchymal neoplasm of intermediate (borderline) malignancy

“…Although granular cell variants of atypical fibroxanthoma have been reported, atypical fibroxanthomas generally lack CD34 expression, show brisk mitotic activity, and arise in the dermis of sun-exposed skin. [17][18][19][20] Finally, we did not detect TP53 overexpression in any studied case; TP53 overexpression is commonly present in high-grade pleomorphic sarcomas, myxofibrosarcomas, and atypical fibroxanthomas. [21][22][23][24][25][26] The superficial location, striking pleomorphism, low mitotic rate, and chronic inflammatory cell infiltrate of superficial CD34-positive fibroblastic tumor might also raise the question of a possible relationship to pleomorphic hyalinizing angiectatic tumor.…”

Atypical Fibroxanthoma of the External Ear: Case Report and Review of Literature

“…2,10,11 The cell type that gives rise to AFX is under debate, with current sources suggesting an undifferentiated mesenchymal cell with features of fibroblastic, myofibroblastic, or histiocytic origin. 2,3,7 The tumor may appear as a pink to red papule or nodule with superficial ulceration and bleeding. 10 Most AFX are less than 2.0 cm in diameter, with a 4 month median interval from onset to presentation.…”

“…No specific immunohistochemical markers identify AFX, but vimentin, CD10, CD68, and p53 are all likely to be positive in cases of AFX. [1][2][3]6,12 It is advisable to order pan cytokeratin stains, pan melanocytic cocktail (HMB-45, anti-Mart 1, anti-tyrosinase), S100, AE1/AE3, P63, smooth muscle actin, CD31, and CD34 to exclude other neoplasms. [1][2][3] While soft tissue sarcomas are graded based on histological appearance, this is not appropriate for AFX because the alarmingly abnormal features would suggest a highgrade tumor although it has intermediate malignant potential at most.…”

“…The initial differential diagnosis included atypical fibroxanthoma, atypical sarcoma, and Atypical fibroxanthoma (AFX) is a tumor that is classically found in elderly Caucasian male patients, with most neoplasms occurring on chronically sun-damaged skin. [1][2][3]9 There are 2 distinct anatomic locations and demographic populations in which these tumors occur. 8 78% of AFX occurs in the sun-exposed head and neck, with a median age of 69 among patients affected.…”

“…[1][2][3][4] A retrospective study on 42,279 skin cancers treated using Mohs micrographic surgery revealed that .24% of these skin cancers were atypical fibroxanthomas, demonstrating the rarity of this neoplasm. 5 This tumor classically affects elderly Caucasian males and most commonly appears as an ulcerated papule or nodule less than 2.0 cm, though variations occur.…”