Can cytology reliably subtype non-small cell lung carcinomas?

Cytology specimens play an important role in the diagnosis and predictive testing of lung cancer. While morphological characterisation of small cell and non-small cell lung carcinomas (NSCLC) on cytology is possible, further subtyping of NSCLC into adenocarcinoma and squamous cell carcinoma morphology is also mandatory in the current era of personalised medicine. Notably, cytology specimens in different forms (fine needle aspiration, exfoliative, and cell block) with or without immunocytochemistry are reliable sources for accurate diagnosis of adenocarcinoma and squamous cell carcinoma as evidenced by numerous studies present in the literature. However, there are instances where subtyping of NSCLC based on morphology alone is challenging on cytology samples, especially non-cell block preparations. In this paper, we will discuss current concepts, advances, and challenges of subtyping NSCLC in cytology specimens.