**5. Pathology**

**MACROSCOPIC:** On gross examination, the tumor appears as a polypoidal, non-encapsulated, red to gray colored mass with spongy appearance. Mean size is 4 cm.

**MICROSCOPIC:** The tumor has a fibrous stroma with abundant blood vessels. The blood vessels are of variable sizes without any organized layout. Elastin fibers in the blood vessels are typically absent while the muscle layer maybe absent, focal (pad-like) or circumferential. This accounts for profuse bleeding in these tumors as these blood vessels are unable to contract to achieve effective hemostasis.

The fibrous stroma has varying amounts of fine and coarse collagen fibers. Plump spindle, angular, or stellate-shaped cells are also seen. Rarely, mast cells may be present. The nuclei of stromal cells generally lack any characteristic features; although, multinucleated pleomorphic cells are not uncommon.

The vascular and fibrous elements vary in proportion within the same tumor and with the tumor age. While the fibrous component is more towards the centre of the tumor, peripheral areas have abundance of vascular elements. Also, newer lesions have predominantly vascular component while long standing tumors are enriched with fibrous tissue.

Embolised specimens show myxoid changes with areas of infarction. Embolic agent can be seen in the tumor vessels. Post flutamide therapy or radiotherapy specimens show a significant increase in fibrous component (**Figure 2**).

**IMMUNOHISTOCHEMISTRY:** Immunohistochemistry (IHC) tests act as ancillary tests for juvenile nasopharyngeal angiofibroma. Various IHC tests are described in the **Table 1**.

#### **Figure 2.**

*Histopathological section of JNA as seen under a microscope. Multiple blood vessels of varying diameters are seen in a fibrous stroma.*


**Table 1.** *Immunohistochemistry (IHC) tests for JNA.*
