Sinonasal papillomas represent the most common group. Benign salivary gland tumours are relatively rare compared to in the major salivary glands.
Sinonasal Papilloma
Sinonasal papillomas are either inverted, oncocytic or exophytic. They arise from the ciliated respiratory epithelium of the nasal cavity and paranasal sinuses and are unique to this region. The epithelium, also called the Schneiderian membrane, has led to these tumours being referred to as Schneiderian papillomas.
Epidemiology
The inverted and exophytic types are more common in men whereas oncocytic papillomas occur with equal frequency in each gender. Oncocytic papillomas are also much less common (< 5%) than the other types.
Aetiology
HPV infection is associated with the inverted and exophytic types. There is no known aetiology of oncocytic papillomas.
Natural History
Although the lesions do not invade directly, they do cause pressure effect on neighbouring bone and can cause it to erode secondarily. The papilloma can fill the nasal cavity and/or paranasal sinus.
Tumour Features
Inverted Papilloma
These tumours expand throughout the nasal cavity. They have a nodular appearance macroscopically. Microscopic examination demonstrates ribbon-like projections of epithelium that penetrates into the stroma of the tumour. Malignancy is seen in about 10% of cases, usually squamous cell carcinoma.
Oncocytic Papilloma
Oncocytic papilloma is a rare form that consists of oncocytic cells (high numbers of mitochondria). The epithelium lining the papillae is usually multilayered columnar type. About 10% of tumours have an associated malignancy.
Exophytic Papilloma
These are generally smaller lesions that are rarely associated with malignancy. In contrast to the other papillomas, they exhibit and exophytic growth pattern. They can be differentiated from more common nasal vestibular keratinising papilloma by the presence of ciliated respiratory epithelium.
Salivary Gland Tumours
These tumours are exceedingly rare; the most common forms of salivary gland tumours in the sinonasal region are malignancy adenoid cystic carcinoma.
