Case 1: Glomangiopericytomas are circumscribed, but unencapsulated. An unencapsulated proliferation of short spindle cells underlies the intact mucosa (upper right).

Perivascular hyalinization is a common and helpful diagnostic feature. The ovoid cells are monotonous with indistinct cell borders, lending a syncytial look.

The vessels may exhibit staghorn morphology, but more commonly round or serpiginous. There is often an inflammatory component consisting of mast cells and eosinophils.

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.

Glomangiopericytoma is now the preferred name for sinonasal-type hemangiopericytomas (HPCs). This is a rare sinonasal neoplasm composed of perivascular myoid-type cells.

Note that these tumors are distinct from solitary fibrous tumors of the sinonasal cavity as well as from soft tissue HPCs. Glomangiopericytomas are indolent tumors and have a better prognosis compared to HPC/SFT of the soft tissues. Additionally, glomangiopericytomas have a true myoid phenotype and stain for actins, (SMA, MSA) and are negative for CD34, CD31 and Factor 8-related antigen. SFTs of the soft tissue and sinonasal cavity are negative for actins and diffusely positive for CD34 (Thompson, Dandekar).

Side note: Hemangiopericytomas (of the soft tissue) is no longer considered a distinct entity by many experts and is simply a term used to describe soft tissue tumors with staghorn and branching vessels -- this feature can be seen in variety of unrelated neoplasms including synovial sarcoma, low-grade endometrial stromal sarcoma and mesenchymal chondrosarcomas. Many of the "cellular hemangiopericytomas" are better classified as solitary fibrous tumors.

Other entities on the differential diagnosis for glomangiopericytomas include: lobular capillary hemangioma (distinct lobular architecture), sinonasal leiomyoma (cells have cigar-shaped nuclei and perinuclear vacuoles and fibrillary cytoplasm), angiofibromas (unique clinical features, abundant stromal collagen)(Dandekar).

In a review of 104 cases of glomangiopericytomas (sinonasal-type hemangiopericytoma) conducted by Thompson et al (2003), there was nearly equal gender distribution (57 females, 47 males) with a mean age of 62. Common presenting symptoms include airway obstruction and epistaxis. The clinical course was largely benign with excellent long-term outlook (>95% 5 year survival).

Treatment is wide surgical excision with free resection margins.

→Glomangiopericytomas of the sinonasal tract used to be called sinonasal-type hemangiopericytoma.

→Glomangiopericytomas demonstrate true myoid (perivascular modified smooth muscle cell) origin.

→In contrast with SFT (that can also occur in the sinonasal-tract), glomangiopericytomas are positive for actins (smooth muscle actin, muscle specific actin) and negative for CD34. SFTs, on the other hand, are positive for CD34 and negative for actins.

→Histologically, glomangiopericytomas have bland ovoid cells arranged with a syncytial pattern with prominent perivascular hyalinization. SFTs have intermixed ropy collagen fibers and lack the prominent perivascular hyalinization.

• Pleura : Solitary Fibrous Tumor