Tumors of the soft tissues

The present manuscript gives emphasis on recognizing different morphological variants of atypical fibroxanthoma (AFX), on validation of immunohistochemical markers and on discussing potential diagnostic pitfalls.



Material and methods: Histological features analyzed in 66 AFXs were: ulceration, morphological variants, growth pattern, location in the skin and vascular/perineural invasion. The antibodies used were CK-MNF116, CK-AE1/AE3, S100, smooth muscle actin, desmin, CD31 and EMA.



Results: The study included 59 males, 7 females, aged 55–95 years, mean 77 years. All developed on sun damaged skin. Ulceration was present in 50%. Morphological patterns were pleomorphic spindle and epithelioid cells (60.6%), predominantly spindle cells (19.7%), purely spindle-cells (13.6%), and predominantly epithelioid cells (6.1%). Most were localized in the dermis (57.6%). An expansile (36.4%) rather than infiltrative (6.1%) growth into superficial subcutis was also noted. No vascular/perineural invasion was seen. Additional changes were hemorrhagic and pseudoangiomatous areas (24.2%), granular cell change (22.7%), keloid-like areas (9.1%), myxoid change (7.6%), osteoclast-like giant cells (6.1%) and clear cell change (4.6%). AFXs were consistently negative for S100, CK-MNF116, CK-AE1/AE3 and desmin. Focal positivity for SMA (45.2%), EMA (24.4%) and CD 31 (9.5%) was seen.



Conclusions: A diagnosis of AFX is still made by exclusion of other malignant neoplasms with similar morphology. Immunohistochemistry plays a crucial role in this distinction, but can also be misleading. This study expands the spectrum of non-vascular CD31 positive tumors.



Luzar B, Calonje E. Morphological and immunohistochemical characteristics of atypical fibroxanthoma with a special emphasis on potential diagnostic pitfalls.

Morphological and immunohistochemical characteristics of atypical fibroxanthoma with a special emphasis on potential diagnostic pitfalls: a review

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.

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

Background Atypical fibroxanthoma (AFX) is an uncommon superficial fibrohistiocytic tumor. It was originally described as a low-grade dermal tumor of atypical spindle cells, but this view has changed, and it is generally considered to be a tumor of intermediate malignant potential. Objective To review the current literature on AFX pertaining to epidemiology, pathogenesis and etiology, clinical presentation, histology, immunohistochemistry, prognosis and follow-up, and treatment. Materials and methods Extensive literature review was conducted using OVID Medline and Pubmed searching for articles relating to AFX. Results AFX typically presents as a red or pink papule or nodule on the head or neck of an elderly man. The pathogenesis is most commonly related to ultraviolet radiation. It can clinically mimic other cutaneous malignancies and histologically can mimic squamous cell carcinoma, desmoplastic melanoma, and undifferentiated pleomorphic sarcoma. Immunohistochemistry is important in making the distinction. The prognosis is generally excellent, although there are rare cases of metastatic disease. There is a higher cure rate with Mohs' micrographic surgery than with wide local excision. CONCLUSIONS People with AFX generally have had significant ultraviolet radiation exposure. They should be examined at least every 6 months for recurrence, metastasis, and the development of additional skin cancers.

Atypical fibroxanthoma: a review of the literature.

Atypical fibroxanthoma (AFX) represents a lowgrade form of sarcoma (or to some simply a low-grade tumor) that is frequently included in differential diagnoses in dermatopathology, commonly investigated and commented upon by dermatopathologists,1– 17 and perhaps a bit misunderstood. In the pages of the JCP, the topic of AFX is not infrequently addressed, as the many references listed below attest. In the past two years, a number of remarkable contributions regarding the biology of AFX have come forward in these pages.1,4,8,10,12,15 The nosology of AFX remains somewhat controversial. Although there is relatively broad consensus that AFX is of fibrocytic (or ‘‘fibrohistiocytic’’) lineage, a minority view that AFX represents dedifferentiated carcinoma perseverates and is probably fueled by the fact that AFX occasionally (rarely) shows aberrant keratin expression,5,17 a phenomenon that has been termed keratin-positive AFX. Although the atypical cells that comprise an AFX often show histiocyte-like morphology with abundant vacuolated cytoplasm, it seems clear that the tumor is unrelated to authentic histiocytes, which are of hematopoietic derivation. Rather, the cells of AFX demonstrate fibrocytic or myofibrocytic differentiation. The fact that procollagen-1 and actin are commonly expressed by AFX supports this conclusion, and ultrastructural attributes also suggest this.1,7,14 The histiocyte-like morphology exhibited by AFX is unsurprising, given the extreme morphological capacity of fibrocytes. The same aptitude for cytological diversity represents a commonality between AFX and other fibrous proliferations, including dermatofibroma. In the paragraphs and sections that follow, recent observations that improve our understanding of the entity with one of the briefest yet most distinctive acronyms in all of dermatopathology will be explored more fully.

AFX: what we now know.

Background: Atypical fibroxanthomas (AFX) are dermal-based cutaneous tumors typically found in sun-damaged skin of the elderly. Histologic variants include spindle cell, clear cell, osteoid, osteoclastic, chondroid, pigmented, and granular cell. To date, myxoid change in AFX, has not been described.

Methods: Four cases were retrieved from the consultation and surgical pathology files of Knoxville Dermatopathology Laboratory, Knoxville, Tennessee during a 4-year period. The clinical and histologic findings were reviewed and Alcian blue/periodic acid-Schiff (PAS) stain and panel of immunohistochemical stains was obtained.

Results: All 4 lesions occurred as solitary lesions in elderly males on the head and neck (2 cases) and upper extremity (2 cases). Histologically all tumors demonstrated a well-circumscribed, cellular lesion centered in the dermis and composed of a mix of atypical pleomorphic and spindle cells in a prominent myxomatous background. A junctional component was absent and the tumors did not arise from the epidermis or adnexal structures. Subcutaneous involvement was absent in all cases. Tumor cells were negative for melanocytic and epithelial markers. Positive staining was noted with CD10 (3/4 cases) and vimentin (4/4 cases).

Conclusion: Myxoid change in AFX is rare and previously undescribed in the English literature. Myxoid change may be a prominent finding in benign and malignant cutaneous tumors and awareness of this variant of AFX will avoid misdiagnosis.

Myxoid atypical fibroxanthoma: a previously undescribed variant.

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Myxoid atypical fibroxanthoma: a previously undescribed variant.