The DEBATE Study "DEvelopment of Endotype-based Biomarkers for the Monitoring of Greek pATiEnts With CRSwNP"

Inclusion Criteria: * Age ≥ 18 years * If CRSwNP group: Physician-diagnosed severe, uncontrolled CRSwNP according to the EUFOREA/EPOS 2020 and ICAR-RS 2021 guidelines with: * CRSwNP severity consistent with the need for surgery as defined by a total nasal polyp score (NPS) of ≥5 (≥2 for each nostril) * Nasal Congestion Score (NCS) of ≥2 * Ongoing documented symptoms of CRSwNP for \> 8 weeks before surgery If CRSsNP group: Diagnosis of CRSsNP according to the EUFOREA/EPOS 2020 and ICAR-RS 2021 guidelines * Have performed in the period between 2012 and enrolment or are scheduled to perform endoscopic sinus surgery (ESS) for the first time at enrolment * Have available nasal polyp tissue sample from the first endoscopic sinus surgery (ESS) * Have provided signed and dated written informed consent * If CRSwNP group: Patients receiving any standard of care treatment for CRSwNP, provided the participant is stable on that treatment for ≥30 days Exclusion Criteria: * Patients with cystic fibrosis or immunodeficiency * Presence of acute exacerbation of CRS symptoms within 2 weeks prior to surgery * Use of systemic corticosteroids within 30 days prior to surgery, or antileukotrienes within 15 days prior to surgery, or biologic therapy prior to surgery * Not adequate amount (\<0.15g) or quality (e.g. storage temperature, contamination) of tissue sample for analyses * Not available blood (serum) sample, only for patients scheduled to perform endoscopic sinus surgery (ESS) for the first time at the date of enrolment, for analyses.