MKI67 and neoplasm: Second, the classification of lung NENs used, while based on current standards, may be subject to change as the classification system is being refined.3,4 This approach did not include tumor grade databased on Ki67 proliferation index, which is consistent with other studies in this field.6 Despite these limitations, the study’s strengths lie in its true population-based design, which allowed for a comprehensive examination of lung NENs incidence and a clinical practice assessment of prognosis.