A Schneiderian papilloma is a non-cancerous tumour that starts from the tissue that lines the inside of the nasal cavity and paranasal sinus. Pathologists divide Schneiderian papillomas into three types: inverted, exophytic, and oncocytic (see below for more information). Schneiderian papillomas can grow into surrounding tissues but the tumour cells are not able to spread to other parts of the body. Another name for Schneiderian papilloma is sinonasal papilloma.
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.
Schneiderian papillomas often grow as finger-like projections outwards and can block the nasal passages. As a result, the tumour can cause symptoms such as:
Schneiderian 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 for developing a type of cancer called squamous cell carcinoma.
Inverted Schneiderian papilloma is the most common type of Schneiderian papilloma. It typically affects adults over the age of 50 years and most arise from 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 Schneinderian 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. Because of this risk, the entire tumour should be removed and sent for pathologic examination.
Exophytic Schneiderian papillomas occur more often in people less than 50 years of age and are twice as common in men than women. The tumour 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.
It is very rare for cancer to develop in this type of papilloma.
Oncocytic Schneiderian papillomas are more common in people over the age of 50 years and affect men and women equally. This type of 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.
Cancer can also develop in this type of papilloma although it is less likely than for the inverted type.
The diagnosis of Schneiderian 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 disease called squamous carcinoma in situ or a type of cancer called squamous cell carcinoma.
If you had surgery to remove the tumour from your body, your pathologist will attempt to measure the tumour and this measurement will be included in your report. For example, if the tumour measures 5 cm x 3 cm x 1 cm, the report may describe the tumour size as 5 cm in the greatest dimension.
Schneiderian papillomas are often removed in multiple pieces. As a result, your pathologist may not be able to accurately measure the tumour size. In this case, an approximate tumour size may be described.
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 Schneiderian 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 Schneiderian papillomas do not have information about margins.
Schneiderian papillomas are non-cancerous tumours. However, over time, the tumour can change and a cancer called squamous cell carcinoma can develop. Carcinoma ex Schneiderian papilloma is the term pathologists use to describe a carcinoma arising from a Schneiderian papilloma.
This cancer often develops from a pre-cancerous disease called squamous carcinoma in situ. Both squamous cell carcinoma and squamous carcinoma in situ are more likely to develop in an inverted type Schneiderian papilloma and they are very rare in the exophytic or oncocytic types.
Squamous cell carcinoma or squamous carcinoma in situ may be seen in a biopsy or only after the entire tumour has been removed. If squamous cell carcinoma is seen, you may be offered additional treatment to reduce the risk that the tumour will regrow or spread to other parts of the body.