Answer: Angiofibroma

Histology: The histopathologic picture is dominated by two components – a vascular component and a fibrous component. The blood vessels have thin walls with absent or incomplete smooth muscle. They are lined by a single layer of endothelial cells. Their lumens may be compressed or open forming staghorn configurations. Some of the vessels may be filled with a pink fibrillary matrix owing to selective embolization prior to surgical resection. The stroma consists of spindled to stellate cells in a collagenized background. One may observe a zonal pattern: the periphery of the lesion may be highly vascular and reminiscent of granulation tissue, while the central portion of the lesion may be more densely collagenized with a paucity of vessels. Mast cells may be sprinkled throughout the lesion, but other types of inflammatory cells are not encountered unless associated with areas of ulceration.

Discussion: Nasopharyngeal angiofibromas are uncommon tumors that typically arise in the nasopharynx/posterior nasal cavity of adolescent males. Their growth and development are hormonally (testosterone) driven. Females rarely if ever develop these tumors. Antrochoanal polyps may involve a similar population of patients, but these typically arise from the maxillary sinus and involve the nasopharynx only by secondary extension. Patients with nasopharygeal angiofibromas clinically present with non-specific signs and symptoms including nasal obstruction and epistaxis.

The histologic hallmark feature of nasopharyngeal angiofibroma is the intimate admixture of thin-walled vessels and fibrocollagenous stroma. The highly vascular advancing edge of a nasopharyngeal angiofibroma may be confused with a lobular capillary hemangioma (LCH). Unlike nasopharyngeal angiofibroma, LCH does not generally involve the nasopharyx, and it lacks the uniform distribution of vessels within a collagenized stroma. Hemangiopericytomas tend to be much more cellular tumors with less intervening collagen. Indeed, the presence of individual stellate cells scattered within a collagenized stroma would be unusual for a hemangiopericytoma.

Surgical removal is the treatment of choice, and tumor recurrence is common following incomplete resection. Because of the characteristic clinical findings, anatomic location and radiographic features, biopsies of these highly vascularized tumors are neither necessary nor indicated. To minimize operative bleeding, selective preoperative embolization is frequently employed. Accordingly, intratumoral thrombosis is a common histologic finding.