by Emilija Todorovic MD FRCPC
June 5, 2022
A sinonasal papilloma is a non-cancerous tumour that starts from the tissue that lines the inside of the nasal cavity and paranasal sinus. Pathologists divide sinonasal papillomas into three types: inverted, exophytic, and oncocytic (see below for more information). Sinonasal papillomas can grow into surrounding tissues but the tumour cells are not able to spread to other parts of the body. Another name for sinonasal papilloma is Schneiderian papilloma.
Sinonasal papillomas often grow as finger-like projections outwards and can block the nasal passages. As a result, the tumour can cause symptoms such as:
Sinonasal papillomas are divided into three types – inverted, exophytic, and oncocytic – based on how the tumour looks when examined under the microscope. The tumour type is important because the inverted type is more likely to grow and damage surrounding tissues if it is not completely removed. The inverted type is also associated with a high risk of developing a type of cancer called squamous cell carcinoma.
Inverted sinonasal papilloma is the most common type of sinonasal papilloma. It typically affects adults over the age of 50 years and most arise in the wall of the maxillary sinus and the lateral wall of the nasal cavity. Less commonly, the tumour will start in the wall of the ethmoid, frontal, or sphenoid sinus.
When examined under the microscope, the tumour is seen growing downwards from the surface mucosa, which is why they are called inverted. The tumour is made up of a combination of squamous cells and mucin-producing mucocytes. Specialized immune cells called neutrophils are also seen.
While it is considered a non-cancerous tumour, an inverted sinonasal papilloma can cause significant damage to surrounding tissues as it grows. This can include the cartilage of the nose and bones of the face. In addition, a small number of inverted papillomas can change over time into a type of cancer called squamous cell carcinoma (see sections below). For these reasons, all inverted type sinonasal papillomas should be removed completely.
Exophytic sinonasal papillomas tend to occur more often in people less than 50 years of age and are twice as common in men than women. It almost always starts on the medial wall of the nasal cavity near the septum.
When examined under the microscope the tumour is seen growing outwards from the surface of the mucosa in long finger-like projections of tissue. Pathologists call these finger-like projections a papillary pattern of growth. The tumour is made up of a combination of squamous cells and mucin-producing mucocytes. Specialized immune cells called neutrophils are also seen.
Oncocytic sinonasal papillomas are more common in people over the age of 50 years and affect men and women equally. This type of sinonasal papilloma is more likely to start on the lateral wall of the nasal cavity although it can also start on the wall of a sinus. When examined under the microscope, the tumour is made up of large pink cells. Pathologists describe these types of cells as oncocytic.
The diagnosis of sinonasal papilloma is usually made after a small tissue sample is removed in a procedure called a biopsy. The tumour is then removed completely in a procedure called a resection. Your pathologist will carefully examine the entire tumour to look for a pre-cancerous change called dysplasia or a type of cancer called squamous cell carcinoma.
Dysplasia is an abnormal pattern of growth that can change into cancer over time. Pathologists divide dysplasia into grade – low grade dysplasia and high grade dysplasia – and the risk of developing cancer is greater when high grade dysplasia is seen.
Although rare, dysplasia can be seen in some sinonasal papillomas. For this reason, the entire sinonasal papilloma needs to be examined closely for any evidence of dysplasia and when seen, it will be described in your pathology report.
Sinonasal papillomas are non-cancerous tumours. However, over time, a cancerous tumour can develop from the cells in a sinonasal papilloma. The most common type of cancer to develop from a sinonasal papilloma is called squamous cell carcinoma. Carcinoma ex sinonasal papilloma is the term pathologists use to describe a cancer such as squamous cell carcinoma that develops from a sinonasal papilloma.
Most cancerous tumours develop from a precancerous change called dysplasia (see Dysplasia section above). Both dysplasia and cancer are more likely to develop in an inverted type sinonasal papilloma and they are very rare in the exophytic or oncocytic types.
Cancerous tumours that develop from a sinonasal papilloma tend to behave in an aggressive fashion. For example, the cancerous tumour is more likely to grow into parts of the head surrounding the sinonasal tract. Similar to other types of cancer, the cells in a cancerous tumour that develops from a sinonasal papilloma are also able to spread to other parts of the body.
A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. Whenever possible, surgeons will try to cut tissue outside of the tumour to reduce the risk that any tumour cells will be left behind after the tumour is removed.
A negative margin means there were no tumour cells at the very edge of the cut tissue. A margin is considered positive when there are tumour cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will grow back (recur) in the same site after treatment.
Because sinonasal papillomas are often removed in multiple pieces, your pathologist may not be able to reliably assess the margins of the tumour. For that reason, most pathology reports for sinonasal papillomas do not have information about margins.