Low tumour cell content in a lung tumour bank: implications for molecular characterisation

Lung cancer encompasses multiple malignant epithelial tumour types, each with specific targetable, potentially actionable mutations, such that precision management mandates accurate tumour typing. Molecular characterisation studies require high tumour cell content and low necrosis content, yet lung cancers are frequently a heterogeneous mixture of tumour and stromal cells. We hypothesised that there may be systematic differences in tumour cell content according to histological subtype, and that this may have implications for tumour banks as a resource for comprehensive molecular characterisation studies in lung cancer. To investigate this, we estimated tumour cell and necrosis content of 4267 samples resected from 752 primary lung tumour specimens contributed to a lung tissue bank. We found that banked lung cancer samples had low tumour cell content (33%) generally, although it was higher in carcinoids (77.5%) than other lung cancer subtypes. Tumour cells comprise a variable and often small component of banked resected tumour samples, and are accompanied by stromal reaction, inflammation, fibrosis, and normal structures. This has implications for the adequacy of unselected tumour bank samples for diagnostic and molecular investigations, and further research is needed to determine whether tumour cell content has a significant impact on analytical results in studies using tissue from tumour bank resources.