Background The development of drugs that target lung adenocarcinoma caused by epidermal growth factor tyrosine kinase (EGFR-TK) and anaplastic lymphoma kinase (ALK) mutations has focused the need to obtain sufficient tissue at biopsy to allow the detection of such molecular markers and so improve treatment options for selected patients. To investigate this further, we looked at the diagnostic yield from various biopsy techniques in our large lung cancer unit (400 cases per year, overall histological yield 77.5%).

Methods We collected data from all patients with an ultimate histological diagnosis of adenocarcinoma for the years 2014 to 2016, looking at the diagnostic method, whether tissue was analysed for molecular mutations, and whether repeat procedures were necessary for EGFR-TK and ALK testing.

Results 224 patients were identified: 42 by EBUS-TBNA, 66 by CT-guided biopsy, 44 at bronchoscopy, 66 at surgical resection, 6 from pleural fluid, and 1 by lymph node FNA. For molecular testing see Table. In addition to those patients where sampling was insufficient to make the diagnosis, a further 30 had inadequate cell numbers for mutation analysis and the reporting pathologist recommended repeat procedures. Of the 10 patients who underwent this, only 2 were retested for molecular markers, and the Results were unchanged.

Conclusion This study shows that all our pre-resection positive diagnostic samples for lung cancer do not always provide sufficient tissue for molecular analysis. Although insufficiency rates were similar between CT, EBUS and bronchoscopy, one third of CT-guided specimens had few cells for the definite exclusion of mutations. With the advent of new therapies for lung cancer, we need to optimise our diagnostic sampling techniques when testing for molecular mutations.