Subtyping of non-small cell lung cancer by cytology specimens: A proposal for resource-poor hospitals

Aim: Cancer diagnosis and treatment depend on pathology reports but naming a cancer is sometimes impossible without specialized techniques. We aimed to evaluate the sensitivity of cytological sub-classification of non-small cell lung carcinoma, not otherwise specified group (NSCLC-NOS) into Adenocarcinoma (AC) and Squamous cell carcinoma (SqCC) without using immunohistochemistry. Methods: Endobronchial ultrasound guided fine-needle aspiration biopsies and cytology slides diagnosed as NSCLC-NOS between 2004-2008 were reviewed retrospectively. The final diagnosis was reached by immunohistochemistry (TTF-1, p63) when necessary. Results: One hundred-Twenty nine cases were retrieved. The final diagnoses were as follows: SqCC: 30.3%; AC: 65.7%; combined tumor (3 adenosquamous and 1 small cell + SqCC): 4%. Cytological diagnoses rendered were as follow: Definitely SqCC: 10.1%; favor SqCC: 14.1%; definitely AC: 38.4%; favor AC: 35.4%; NSCLC-NOS: 2%. The sensitivity and specificity of cytology were 86.3 and 87.5% for AC diagnosis respectively. Conclusion: Positive and negative predictive value of cytology was 95.3% and it was even 100% for well to moderately differentiated tumors. There was a tendency to sub-classify poorly differentiated SqCC as AC. Papanicolaou stain increased the diagnostic accuracy of SqCC. The combined tumor rate was 4% and after recognizing a tumor component, the second component was missed if the slide examination was terminated prematurely.