Diagnostic accuracy in the subclassification of non-small cell lung carcinomas in bronchial cytology specimens

Abstract

Lung cancer is the most common cancer and also a leading cause of cancerrelated mortality worldwide. Accurate classification of non-small cell lung cancer (NSCLC) into squamous cell carcinoma (SCC) and adenocarcinoma (ACA) is becoming increasingly important with the advent of new targeted therapeutic agents. The reliability of the cytology diagnostic service in NSCLC classification has not been locally assessed to date. This study thus aimed to assess cytological diagnostic accuracy and determine the significance of several cytomorphological features in NSCLC classification. Residual material from bronchial lavage specimens received between June 2011 and December 2012, and diagnosed as ACA or SCC, was used for cell block preparation, histological processing and Haematoxylin and Eosin (H&E) staining. Cell blocks having adequate cellularity on H&E were selected for immunohistochemical (IHC) staining, used as the reference method for classification. Twenty (20) further cases diagnosed during 2011 and 2012 and having IHC results were retrospectively retrieved, amounting to a total of 48 cases. Corresponding Papanicolau stained slides were examined for a variety of cytomorphological features by two independent observers. Upon comparison of cytology and IHC results, inter-observer agreement was found to be substantial (κ=0.705) and the overall cytological diagnostic accuracy was 88.9%. The most significant cytomorphological features in distinguishing SCC cases were found to be orangeophilic cytoplasm and spindle cells; for ACA the presence of foamy cytoplasm was most significant. Diagnostic accuracy of NSCLC sub-typing by cytomorphology alone is high, especially in SCC cases; ancillary techniques such as IHC retain their importance in sub-optimal cases.