Angiomatoid fibrous histiocytoma: pleomorphic variant associated with multiplication of EWSR1-CREB1 fusion gene.

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor which exceptionally occurs in visceral organs or bones. Histologically this is a bland, monomorphic tumor and only occasionally shows pleomorphism. Vast majority of the soft tissue cases share the same translocation and the resulting EWSR1-CREB1 gene fusion as background pathogenetic alteration. Here we report a 10-year-old boy with subcutaneous tumor of the right shoulder. Histological, immunohistochemical and FISH analyses of the case revealed pleomorphic phenotype, characteristic immunophenotype and multiplication of the EWSR1-CREB1 fusion gene in the nuclei of the tumor cells. The possible explanation of the fusion gene multiplication, its relation to the morphology and the clinical outcome are discussed in the context of the published literature.