The primary purpose of this non-interventional, multinational study is to assess the feasibility of assessing PD-L1 protein expression on cytological samples as a surrogate for histological samples obtained from participants with any stage of non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC).

Inclusion Criteria:

• Samples must have been collected in a manner that is compliant with local ethics committee guidance
• Samples must originate from participants diagnosed with NSCLC or SCLC
• Participants must have a pair of at least one cytological and one histological specimen that: Both originate from inside the thorax or from the same ex-thoracic site; Are confirmed to have been collected within a window no more than 6 weeks apart from each other; and are in compliance with the protocol defined sample requirements for histological and cytological specimens

Exclusion Criteria:

• Immune checkpoint inhibitor therapy from 4 weeks prior to collection of the first tumor sample until collection of the second matched sample

Participants with any stage of NSCLC or SCLC who have cytological and histological samples available.