The Orbital Hemangiopericytoma: The Number of Reported Cases and a Possible Risk Factor

I read, with interest, the article entitled "The Orbital and Sinonasal Hemangiopericytoma, 2 Case Reports" by Maryam Maghbol et al. published in this journal. I would like to draw attention to the number of reported orbital hemangiopericytomas and a possible risk factor for this tumor. Accordingly, in the discussion and conclusion section, the authors claimed that thirty-three cases of orbital hemangiopericytomas already has been published. However, with regard to the literature, at least 50 cases of this tumor already has been published. Moreover, the authors affirm that no specific risk factor already has been recognized for this tumor. In a study stated that previous trauma has a possible role in the origin of hemangiopericytomas.