"Ia: limited to nasal cavity/nasopharynx"
"Ib: extension into one or more paranasal sinuses"
"IIa: minimal extension through sphenopalatine foramen into pterygopalatine fossa"
"IIb: fills pterygopalatine fossa bowing the posterior wall of the maxillary antrum anteriorly or extending into the orbit via the inferior orbital fissure"
"IIc: extends beyond pterygopalatine fossa into infratemporal fossa (modified by Radkowski 4)"
"stage III: intracranial extension"