Sinonasal Papilloma: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 14, 2026

A sinonasal papilloma is a noncancerous (benign) tumor that starts from the tissue lining the inside of the nasal cavity and paranasal sinuses. Another name for it is Schneiderian papilloma. Pathologists divide sinonasal papillomas into three types, called inverted, exophytic, and oncocytic, based on how the tumor looks under the microscope. Sinonasal papilloma is not a cancer, and the tumor cells do not spread to other parts of the body. However, it can grow into and damage surrounding tissues, and one type (the inverted type) carries a small risk of turning into a cancer over time, which is why complete removal and follow-up are important. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes a sinonasal papilloma?

The exact cause of sinonasal papilloma is not fully understood. Some of these tumors, particularly the exophytic type, are associated with infection by low-risk types of human papillomavirus (HPV). Researchers have also found that the different types tend to carry different genetic changes: most inverted papillomas have a change in a gene called EGFR, while oncocytic papillomas often have a change in a gene called KRAS. These changes are mainly of interest to pathologists in understanding the tumor and are not something patients need to act on.

What are the symptoms?

Sinonasal papillomas often grow as finger-like projections that can block the nasal passages, so symptoms are usually related to nasal obstruction and irritation. Common symptoms include a blocked or runny nose, nosebleeds, recurrent infections, pain, and headache. Because these symptoms overlap with common conditions such as sinus infections, the diagnosis is usually made only after a tissue sample is examined under the microscope.

Types of sinonasal papilloma

Sinonasal papillomas are divided into three types based on how the tumor looks under the microscope. The type matters because it affects where the tumor tends to occur, how likely it is to grow back, and whether it carries a risk of turning into cancer.

Inverted type

Inverted sinonasal papilloma is the most common type. It typically affects adults over the age of 50, and most start in the wall of the maxillary sinus and the lateral (outer) wall of the nasal cavity; less commonly, the tumor starts in the wall of the ethmoid, frontal, or sphenoid sinus. Under the microscope, the tumor grows downward from the surface mucosa, which is why it is called “inverted.” It is composed of squamous cells and mucin-producing cells (mucocytes), along with scattered immune cells such as neutrophils. Although it is noncancerous, an inverted papilloma can damage surrounding tissues as it grows, including the cartilage of the nose and the bones of the face. A small number of inverted papillomas (about 5 to 10 percent) can change over time into a cancer called squamous cell carcinoma. For these reasons, inverted papillomas should be removed completely.

Exophytic type

Exophytic sinonasal papilloma tends to occur in people under 50 and is about twice as common in men as in women. It almost always starts on the medial (inner) wall of the nasal cavity near the septum. Under the microscope, the tumor grows outward from the mucosal surface in long, finger-like projections, a pattern pathologists call papillary. Like the inverted type, it is made up of squamous cells and mucin-producing mucocytes, with scattered neutrophils. The exophytic type only rarely turns into cancer.

Oncocytic type

Oncocytic sinonasal papilloma is more common in people over the age of 50 and affects men and women equally. It most often starts on the lateral wall of the nasal cavity, although it can also start on a sinus wall. Under the microscope, it consists of large pink cells that pathologists describe as oncocytic. Like the inverted type, the oncocytic type carries a small risk of turning into cancer over time.

How is the diagnosis made?

The diagnosis of sinonasal papilloma is made after a tissue sample is examined under the microscope by a pathologist. A small sample is usually first removed in a procedure called a biopsy, often through the nose using an endoscope. Under the microscope, all three types of sinonasal papilloma are made up of a thickened lining containing squamous cells and mucin-producing mucocytes, usually with scattered neutrophils. What distinguishes the types is the way the tumor grows: downward into the underlying tissue (inverted), outward in finger-like projections (exophytic), or as sheets of large pink oncocytic cells. Imaging studies such as CT and MRI are used to show the size and location of the tumor and to help plan its removal. The tumor is then usually removed completely in a procedure called a resection.

Dysplasia and the risk of cancer

Some sinonasal papillomas develop a precancerous growth pattern called dysplasia. Dysplasia matters because if left untreated, a papilloma with dysplasia can progress to squamous cell carcinoma over time. Of the three types, the inverted type is the most likely to develop dysplasia.

If dysplasia is present, it will be described in your report, and the pathologist will usually grade it using one of two systems. One system divides dysplasia into two grades, low and high. The other divides it into three grades, mild, moderate, and severe. The risk of developing cancer is greatest when high-grade or severe dysplasia is seen. Grading the dysplasia helps your treatment team decide how closely to monitor you after the tumor is removed.

Surgical margins

A surgical margin is the edge of the tissue that the surgeon cuts through when removing the tumor. Whenever possible, surgeons try to remove a rim of normal tissue around the papilloma to reduce the chance that any tumor cells are left behind. Because sinonasal papillomas are often removed in more than one piece, the pathologist may not be able to reliably assess the margins, and many pathology reports for these tumors do not include margin information.

Negative margin — No tumor cells are present at the cut edge of the tissue. This suggests the tumor was completely removed.
Positive margin — Tumor cells are present at the cut edge. This is associated with a higher risk of the tumor growing back (recurrence) in the same area, and it may prompt the treatment team to consider further surgery.

What happens after the diagnosis?

Sinonasal papilloma is treated by removing the tumor completely with surgery, often performed endoscopically through the nose. Because it is noncancerous, chemotherapy and radiation therapy are not used for a sinonasal papilloma on its own. Complete removal is important because these tumors, especially the inverted type, can grow back if any tumor cells are left behind.

After surgery, long-term follow-up is recommended. This is for two reasons: the tumor can recur, sometimes years later, and a small number of inverted and oncocytic papillomas can change into squamous cell carcinoma over time. Follow-up usually includes periodic endoscopic examination of the nasal cavity and sometimes imaging, so that any recurrence or change can be detected and treated early. If cancer is found within a papilloma, treatment is directed at the cancer and is planned by a team that may include ear, nose, and throat (ENT) surgeons, radiation oncologists, and medical oncologists.

Questions to ask your doctor

What type of sinonasal papilloma did I have — inverted, exophytic, or oncocytic?
Was the tumor completely removed?
Was any dysplasia found, and if so, was it low- or high-grade (or mild, moderate, or severe)?
Was any cancer found within the papilloma?
What is my risk of the tumor growing back?
Given my type of papilloma, what is my risk of it turning into cancer over time?
How will I be monitored after surgery, and for how long?
What symptoms should prompt me to contact my doctor between visits?
Will I need any imaging as part of my follow-up?
Which specialists will be involved in my care?