The progress in lung cancer treatment is closely interlinked with the progress in diagnostic methods. There are four steps before commencing lung cancer treatment: estimation of the patient's performance status, assessment of disease stage (tumour, node, metastasis), recognition of histological subtype, and detection of biomarkers. The resection rate in lung cancer is 70% of patients need systemic therapy, which is individually adjusted. Accurate histological diagnosis is very important and it is the basis of further molecular diagnosis. In many cases only small biopsy samples are available and the rules for their assessment are defined in this review. The use of immunochemistry with at least thyroid transcription factor 1 (TTF1) and p40 is decisive in distinction between lung adenocarcinoma and squamous cell carcinoma. Molecular diagnosis and detection of known driver mutations is necessary for introducing targeted therapy and use of multiplex gene panel assays using next-generation sequencing is recommended. Immunotherapy with checkpoint inhibitors is the second promising method of systemic therapy with best results in tumours with high programmed death-ligand 1 (PD-L1) expression on cancer cells. Finally, the determination of a full tumour pattern will be possible using artificial intelligence in the near future.
