Case 2: Normal intact sinonasal respiratory epithelium overlies the tumor.

The spindle cells have bland oval nuclei and are arranged in a vague fascicles.

Diffuse SMA staining supports the myoid origin of these cells.

Case 3: Another case with a monotonous proliferation of ovoid cells. Extravasated RBCs are a common finding.

Scattered inflammatory cells are common. Note that in contrast to solitary fibrous tumors, collagen fibers are not a prominent feature.

The vessels may be staghorn-shaped or simply irregular.

Perivascular hyalinization is a helpful finding seen in the majority of glomangiopericytomas, however, in this case, the hyalinization is a bit subtle.