Paranasal sinus and nasal cavity cancers result from an accumulation of malignant cells in the paranasal sinuses - hollow, air-filled spaces in the bones near the nose – and/or the nasal cavity (the tissue comprising the nasal passages leading from the nostrils to the back of the nose into the throat).  The paranasal sinuses are divided into four types, which are named after the bones that surround them:

• Frontal sinuses - in the lower forehead above the nose
• Maxillary sinuses - in the cheekbones on either side of the nose
• Ethmoid sinuses - beside the upper nose, between the eyes
• Sphenoid sinuses - behind the nose, in the center of the skull

Most cancers of the paranasal sinuses are found in the maxillary sinuses.  Like other head and neck cancers, these cancers may originate from a variety of different types of cells. The cellular classification of the cancer is important in determining prognosis and treatment options.