Glomangiopericytoma and glomus tumor of the sinonasal tract: A report of two cases with emphasis on the differential diagnosis

To the Editor Glomangiopericytoma (GPC; also known as sinonasal typehemangiopericytoma) is very rare, comprising <0.5% of sinonasal tumors. It belongs to the category of borderline and low malignant potential tumors of soft tissues in the nose and paranasal sinuses according to the World Health Organization. GPCs show true pericytic myoid differentiation with consistent expression of smooth muscle actin (SMA). Glomus tumors (GTs) are benign mesenchymal neoplasms and usually originate in the glomus bodies, which are abundant in the distal extremities. GTs of the nose and paranasal sinus are extremely rare. To our knowledge, no more than 30 cases occurring in the sinonasal tract have been reported in the literature. Some authors have speculated a possible relationship between GPC and GT. A previous study reported that GPC is biologically close or identical toGTbased on the striking similarities in the histological appearances and immunophenotypes of these tumors. Recently, it was proposed that mutational activation of beta-catenin and the associated overexpression of cyclin D1 may be key events in the pathogenesis of GPC. Additionally, nuclear accumulation of beta-catenin is a diagnostic marker for GPC and can be a useful discriminator. Here, we report one case each of GPC andGT of the sinonasal tract, and compare their clinicopathologic and immunohistochemical findings.