Sinonasal hemangiopericytomas: clinicopathologic and imaging findings.

Hemangiopericytomas are rare soft-tissue neoplastic lesions that can arise in any part of the body. They are mesenchymal tumors that account for 3 to 5% of all soft-tissue sarcomas and 1% of all vascular tumors. They originate in extravascular cells (pericytes).

Imaging findings of expansile lesions of the thymus.

The purpose of this article is to review the imaging findings of the different expansile lesions of the thymus. Almost 50% of all mediastinal masses are located in the anterior mediastinum. The thymus is the most common site of origin of these masses.

Inflammatory pseudotumor of the trachea.

"Inflammatory pseudotumor" is a broad descriptive term used to describe a localized collection of inflammatory and fibroblastic cells. It is an uncommon lesion that can mimic a tumor when it is located intraluminally in the trachea or bronchi. Because an inflammatory pseudotumor has an abundance of polyclonal plasma cells, its etiology (postinflammatory vs immunologic) is still being debated.