Angiomatoid fibrous histiocytoma: an atypical brain location newly described as intracranial mesenchymal tumor FET-CREB fusion-positive

Excerpt

Angiomatoid fibrous histiocytoma (AFH) was first described in 1979 by Enzinger as an unusual fibrohistiocytic sarcoma in the extremities of young people [1]. According to the Soft Tissues and Bone Tumours World Health Organization (WHO) classification, AFH is characterized by four histopathological criteria: solid nodules of tumoral cells arranged in a syncytial pattern, focal hemorrhages or pseudoangiomatous spaces, a thick fibrous pseudocapsule and a pericapsular rim of lymphoplasmacytic cells with germinal centers [2]. The first case of intracranial AFH was described by Dunham et al. in 2008 [3]. Molecular analysis confirmed the presence of an EWSR1–ATF1 fusion transcript. The recent new WHO classification of Central Nervous System Tumours incorporated this tumor as “intracranial mesenchymal tumor FET-CREB fusion-positive”. Microscopic features are very similar, except for architectural variations from syncytial or sheet-like growth to reticular cord-like structures, with a subset of tumors contain fibrous septa separating nodules of tumor cells. As a rule, these tumors express EMA, CD99, Desmin, Vimentin, CD68 and CD163 [4]. Histopathology can also suggest a meningioma due to the appearance of the cells on microscopy and immunohistochemical positivity for epithelial membrane antigen (EMA). The molecular characteristics are now included as part of the routine diagnostic workup. …