Sinus cancer. Image 1 of 2. Endoscope view of a cancerous growth (white) in the junction between the ethmoid and maxillary sinuses (two of the air-filled cavities that lie behind the face). Cancer cells divide rapidly in a chaotic manner, forming clumps (tumours) that may spread and destroy surrounding tissues. This tumour is growing towards one of the openings of the nasal cavity (choana, upper left), and could block the patient's airway if left untreated. Treatments for cancer include radiotherapy, chemotherapy (anti- cancer drugs) and surgical removal of the cancerous cells. For a view of the tissues after chemotherapy treatment, see image M131/385.