Fig. 1

Flowchart of tumors included in the study. Tumors were excluded when: linking of the databases resulted in no matches or not very reliable matches. It was impossible to screen all records adequately, therefore, of every inclusion year (2010–2014) 50% of the pathology data were extracted of pathology reports. CIS patients were excluded. Only patients with invasive primary laryngeal squamous cell carcinoma with microscopy texts were included. Representativeness of the sample compared to the cohort was analyzed (Supplementary Table 1)