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

Authors


Eduardo Calonje, Department of Dermatopathology, St John's Institute of Dermatology, St Thomas's Hospital, Lambeth Palace Road, London SE1 7EH, United Kingdom
Tel: +44 (0) 20 7188 6408
Fax: +44 (0) 20 7188 6382
e-mail: jaime.calonje@kcl.ac.uk

Abstract

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.

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