Plexiform fibrohistiocytic tumour with novel phenotypic features.

Plexiform fibrohistiocytic tumour is a recently described type of fibrohistiocytic tumour, the differentiation pattern of which is poorly understood. A case representing the predominantly fibrohistiocytic type of the tumour is reported. Immunohistochemical analysis supports the histiocytic origin of this entity. The expression of EBM/11 and tissue transglutaminase both in fibroblast-like and histiocyte-like cells indicate that a single cell line produces the dual morphological features. It is proposed that a non-phagocytic epithelioid pattern of histiocytic differentiation characterizes this tumour.