A sinonasal inflammatory polyp is a non-cancerous growth that may develop in the nasal cavity or paranasal sinuses. Sinonasal inflammatory polyps can be caused by anything that leads to chronic inflammation in the nasal cavity and paranasal sinuses including allergies, upper respiratory tract infections, cystic fibrosis, aspirin intolerance, and diabetes.
When we breathe, air enters our body through our nose and mouth and travels down a long tube called the trachea into our lungs. The inside of the nose is called the nasal cavity and it helps to warm and clean the air before it reaches our lungs.
The nasal cavity is surrounded by small paired (there is on each side of the face) air-filled spaces called paranasal sinuses that connect to the nasal cavity by small openings. Because the nasal cavity and sinuses are connected to each other, pathologists describe this area of the body as the sinonasal tract. The paranasal sinuses include the maxillary sinus, frontal sinus, ethmoid sinus, and sphenoid sinus.
The inside of the nasal cavity and the paranasal sinuses are lined by specialized epithelial cells that form a barrier called the epithelium. The tissue underneath the epithelium is called stroma and it is made up of blood vessels and small round structures called glands that make a substance called mucin. The epithelium and underlying stroma combine to create a layer of tissue called sinonasal mucosa.
The diagnosis of sinonasal inflammatory polyp is usually made after part or all of the polyp is removed in a procedure called an excision. When only small pieces of tissue are removed the procedure may be called a biopsy.
In order to make this diagnosis, a pathologist needs to examine the tissue sample under the microscope. When examined under the microscope, the polyp is usually made up of one or more round pieces of tissue. Pathologists call these polyps because they stick out from the surface of the tissue. The cells on the outside of the polyp are the same type found in the normal sinonasal epithelium. Large numbers of specialized inflammatory cells including neutrophils, eosinophils, plasma cells, and lymphocytes are typically seen within the stroma. The stroma also tends to look white under the microscope because it is full of fluid. This type of change is called edema. The number of glands in the stroma is also typically decreased.