A case of atypical fibrous histiocytoma with positivity for CD163 and CD44

Abstract

Atypical fibrous histiocytoma (AFH) is a variant of dermatofibroma (DF) that was first described by Fukamizu et al. (1) in 1983. Histologically AFH is characterized by proliferation of dermal spindle cells composed mainly of atypical histiocytic cells with striking nuclear pleomorphism and atypia, in a background of classic fibrous histiocytoma (2). It is known that many cases of AFH follow a benign course if complete excision is carried out (2, 3). However, because the tumour cells are atypical, AFH must be differentiated from tumours of intermediate malignancy, such as dermatofibrosarcoma protuberans (DFSP) or atypical fibrous xanthoma (AFX), as well as more malignant tumours, such as pleomorphic dermal sarcoma (PDS)/malignant fibrous histiocytoma (MFH). We report here a case of AFH on the left upper arm of a 63-year-old woman and describe its immunoreactivity in detail. We also discuss the points of histological and immunohistological differentiation between AFH and other cutaneous spindle cell tumours. © 2013 Acta Dermato-Venereologica.