癌細胞仍然在肺或支氣管內膜中,但這些細胞尚未發展成真正的腫瘤。這也稱為原位癌9。
9. ACS. Lung Cancer Staging. 7th Edition. Available at: http://cancerstaging.org/references-tools/quickreferences/documents/lungmedium.pdf. Accessed: 2 May 2019.