Krouse staging
Sinonasal IPs were staged using the Krouse system. Most patients (58.5%) in our cohort presented with Krouse stage 3 – this is when the tumour invades lateral, inferior, superior, anterior, or posterior walls of the maxillary sinus and/or frontal sinus. (1,2) Table 2 summarises the rate of recurrences according to different Krouse stages. The highest rates of recurrence were seen in stage 3, reflecting the more advanced presentation of the cases, especially in secondary cases. (Table 2)